Display device and head mount display device

ABSTRACT

A display device includes a display panel including a substrate and a plurality of display elements disposed on the substrate, and a diffraction panel including a plurality of diffraction patterns disposed on a path of light emitted from the plurality of display elements. The plurality of diffraction patterns are disposed in a first direction to have a first period, each of the plurality of diffraction patterns includes a first refractive layer, a second refractive layer disposed on the first refractive layer, and a third refractive layer disposed on the second refractive layer, and a refractive index of the second refractive layer is higher than a refractive index of the first refractive layer and a refractive index of the third refractive layer.

This application claims priority to Korean Patent Application No.10-2017-0122646, filed on Sep. 22, 2017, and all the benefits accruingtherefrom under 35 U.S.C. § 119, the content of which in its entirety isherein incorporated by reference.

BACKGROUND 1. Field

Exemplary embodiments of the invention relate to a display device and ahead mount display device.

2. Description of the Related Art

Display devices are becoming increasingly important with the developmentof multimedia. In response to this, various types of display devicessuch as a liquid crystal display (“LCD”), an organic light-emittingdiode (“OLED”) display, and the like are being used.

Among the display devices, the OLED display displays an image using anOLED that generates light by recombining electrons and holes. The OLEDdisplay has a high response speed, a high luminance, a wide viewingangle, and low power consumption.

A head mount display device may be mounted on a user's head, and mayhave a form of a pair of glasses, a helmet, or the like. The head mountdisplay device displays an image in front of user's eyes so that theuser may recognize the image.

SUMMARY

Exemplary embodiments of the invention provide a display device capableof increasing an effective light emission area ratio, and a head mountdisplay device.

In addition, exemplary embodiments of the invention provide a displaydevice capable of reducing reflectance due to external light, and a headmount display device.

Further, exemplary embodiments of the invention provide a display devicecapable of minimizing a degree of visual blurring recognition, and ahead mount display device.

Furthermore, exemplary embodiments of the invention provide a head mountdisplay device capable of improving a screen door effect.

It should be noted that objects of the invention are not limited to theabove-described objects, and other objects of the invention will beapparent to those skilled in the art from the following descriptions.

An exemplary embodiment of the invention discloses a display deviceincluding a display panel including a substrate and a plurality ofdisplay elements disposed on the substrate, and a diffraction panelincluding a plurality of diffraction patterns disposed on a path oflight emitted from the plurality of display elements. The plurality ofdiffraction patterns may be disposed in a first direction to have afirst period, each of the plurality of diffraction patterns comprises afirst refractive layer, a second refractive layer disposed on the firstrefractive layer, and a third refractive layer disposed on the secondrefractive layer, and a refractive index of the second refractive layermay be higher than a refractive index of the first refractive layer anda refractive index of the third refractive layer.

An exemplary embodiment of the invention also discloses a display deviceincluding a substrate, a display panel including a plurality of displayelements disposed on the substrate, and a diffraction panel including aplurality of diffraction patterns disposed on a path of light emittedfrom the plurality of display elements. The plurality of diffractionpatterns may be disposed in a first direction to have a first period,each of the plurality of diffraction patterns may include a first layerand a second layer disposed on the first layer, and a refractive indexof the first layer may be higher than a refractive index of the secondlayer.

An exemplary embodiment of the invention also discloses a head mountdisplay device including a display unit including a plurality of displayelements and a plurality of diffraction patterns disposed on a path oflight emitted from the plurality of display elements, and a lens unitdisposed on a path of light emitted from the display unit. The pluralityof diffraction patterns may be disposed in a first direction to have afirst period, each of the plurality of diffraction patterns includes afirst refractive layer, a second refractive layer disposed on the firstrefractive layer, and a third refractive layer disposed on the secondrefractive layer, and a refractive index of the second refractive layermay be higher than refractive indexes of the first refractive layer andthe third refractive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the invention will become more apparentby describing exemplary embodiments thereof in detail with reference tothe attached drawings, in which:

FIG. 1A is a cross-sectional view schematically illustrating anexemplary embodiment of a display device according to the invention, andFIG. 1B is an enlarged view of a portion of the display device;

FIG. 2 shows plan and cross-sectional views illustrating a first pixelunit illustrated in FIG. 1;

FIG. 3A is a perspective view illustrating a base layer and a pluralityof diffraction patterns illustrated in FIG. 1A, and FIG. 3B is anenlarged view of a diffraction pattern;

FIG. 4 is a plan view illustrating the base layer and the plurality ofdiffraction patterns illustrated in FIG. 1;

FIG. 5 is a cross-sectional view taken along line 12-12′ illustrated inFIG. 4;

FIG. 6 is a cross-sectional view taken along a first imaginary lineillustrated in FIG. 5;

FIGS. 7A to 7C are views for describing an exemplary embodiment of anenlargement of an effective light emission area of the display deviceaccording to the invention;

FIG. 8 is a view for describing a reduction of reflectance of lightincident on a first diffraction pattern illustrated in FIG. 1;

FIGS. 9A and 9B show graphs illustrating an exemplary embodiment ofreflectance of an organic light-emitting diode (“OLED”) displayaccording to the invention;

FIGS. 10(a) to 10(c) show graphs illustrating luminance according to avalue of d1/DP1 for each light emission color of an OLED;

FIGS. 11(a) to 11(c) are graphs obtained by normalizing luminance of afirst replicated light emission pattern and luminance of a fifthreplicated light emission pattern on the basis of luminance of areference light emission pattern in FIGS. 10(a) to 10(c);

FIGS. 12(a) to (c) shows graphs illustrating luminance according to avalue of U for each light emission color;

FIGS. 13(a) to 13(c) are graphs obtained by normalizing luminance of afirst replicated light emission pattern and luminance of a fifthreplicated light emission pattern on the basis of luminance of areference light emission pattern in FIGS. 12(a) to 12(c);

FIGS. 14(a) and 14(b) show views for describing an enlargement of anexemplary embodiment of an effective light emission area of lightemitted from an OLED, which emits red light, of the display deviceaccording to the invention;

FIGS. 15(a) and 15(b) show views for describing an enlargement of anexemplary embodiment of an effective light emission area of lightemitted from an OLED, which emits green light, of the display deviceaccording to the invention;

FIGS. 16(a) and 16(b) shows views for describing enlargement of anexemplary embodiment of an effective light emission area of lightemitted from an OLED, which emits blue light, of the display deviceaccording to the invention;

FIG. 17 is a view for describing factors that affect a first diffractiondistance;

FIG. 18 is a plan view illustrating pixel arrangement of a plurality ofpixel units included in a display panel illustrated in FIG. 1;

FIG. 19A is a cross-sectional view illustrating another exemplaryembodiment of a display device according to the invention, and FIG. 19Bis an enlarged view of a portion of the display device;

FIG. 20 is a cross-sectional view illustrating still another exemplaryembodiment of a display device according to the invention;

FIGS. 21 to 23 are views for describing another exemplary embodiment ofa diffraction panel illustrated in FIG. 1;

FIGS. 24A to 27 are cross-sectional views illustrating another exemplaryembodiment of the plurality of diffraction patterns illustrated in FIG.1;

FIG. 28 is a cross-sectional view illustrating another exemplaryembodiment of a display device according to the invention;

FIGS. 29 and 30 are cross-sectional views illustrating other exemplaryembodiments of display devices according to the invention;

FIGS. 31A and 31B are views illustrating a head mount display deviceincluding the display device illustrated in FIG. 1;

FIG. 32 is a view illustrating a conventional technology of a screendoor phenomenon in a head mount display device;

FIG. 33 is a view illustrating an exemplary embodiment of an improvedscreen door phenomenon in the head mount display device according to theinvention; and

FIG. 34 is a view illustrating another exemplary embodiment of a headmount display device according to the invention.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments. It is apparent, however,that various exemplary embodiments may be practiced without thesespecific details or with one or more equivalent arrangements. In otherinstances, well-known structures and devices are shown in block diagramform in order to avoid unnecessarily obscuring various exemplaryembodiments.

In the accompanying drawing figures, the size and relative sizes oflayers, films, panels, regions, etc., may be exaggerated for clarity anddescriptive purposes. Also, like reference numerals denote likeelements.

When an element or layer is referred to as being “on,” “connected to,”or “coupled to” another element or layer, it may be directly on,connected to, or coupled to the other element or layer or interveningelements or layers may be present. When, however, an element or layer isreferred to as being “directly on,” “directly connected to,” or“directly coupled to” another element or layer, there are no interveningelements or layers present. For the purposes of this disclosure, “atleast one of X, Y, and Z” and “at least one selected from the groupconsisting of X, Y, and Z” may be construed as X only, Y only, Z only,or any combination of two or more of X, Y, and Z, such as, for instance,XYZ, XYY, YZ, and ZZ. Like numbers refer to like elements throughout. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

Although the terms first, second, etc. may be used herein to describevarious elements, components, regions, layers, and/or sections, theseelements, components, regions, layers, and/or sections should not belimited by these terms. These terms are used to distinguish one element,component, region, layer, and/or section from another element,component, region, layer, and/or section. Thus, a first element,component, region, layer, and/or section discussed below could be termeda second element, component, region, layer, and/or section withoutdeparting from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, may be used herein for descriptive purposes, and,thereby, to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the drawings. Spatiallyrelative terms are intended to encompass different orientations of anapparatus in use, operation, and/or manufacture in addition to theorientation depicted in the drawings. For example, if the apparatus inthe drawings is turned over, elements described as “below” or “beneath”other elements or features would then be oriented “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below. Furthermore, the apparatus maybe otherwise oriented (e.g., rotated 90 degrees or at otherorientations), and, as such, the spatially relative descriptors usedherein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Various exemplary embodiments are described herein with reference tosectional illustrations that are schematic illustrations of idealizedexemplary embodiments and/or intermediate structures. As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should not beconstrued as limited to the particular illustrated shapes of regions,but are to include deviations in shapes that result from, for instance,manufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionprovided by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the drawings are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and will not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

Hereinafter, exemplary embodiments will be described with reference tothe accompanying drawings.

FIG. 1A is a cross-sectional view schematically illustrating a displaydevice according to an exemplary embodiment of the invention, and FIG.1B is an enlarged view of a portion of the display device.

Referring to FIG. 1A, a display device 10 according to the exemplaryembodiment of the invention may include a display panel 100 and adiffraction panel 200. In this specification, a component which iscoupled to another component through an adhesive member is expressed asa “panel.” In addition, a component which is provided through acontinuous process with another component is expressed as a “layer.” Thepanel includes a base layer providing a base surface. In contrast, in alayer, a base layer may be omitted. That is, when a component isexpressed as a “layer,” the component may be disposed on a base surfaceprovided by another component. Here, in an exemplary embodiment, thebase layer may include a synthetic resin film, a composite materialfilm, a glass substrate, or the like, for example.

The display panel 100 is defined as a panel which displays an image. Tothis end, the display panel 100 may include a plurality of displayelements. Here, in an exemplary embodiment, the plurality of displayelements may be organic light-emitting diodes (“OLEDs”). Accordingly,the display panel 100 may be an OLED display panel. However, a type ofthe display panel 100 is not limited to the OLED display panel and mayvary according to a type of the display element. In an exemplaryembodiment, the display panel 100 may be a quantum dot display panel, aliquid crystal display (“LCD”) panel, or the like, for example.Hereinafter, the display panel 100 will be described as an OLED displaypanel, for example.

A first substrate 110 may be an insulating substrate. In an exemplaryembodiment, the first substrate 110 may include a material such asglass, quartz, a polymer resin, or the like. In an exemplary embodiment,the polymer material may include polyethersulphone (“PES”), polyacrylate(“PA”), polyarylate (“PAR”), polyetherimide (“PEI”),polyethylenenapthalate (“PEN”), polyethyleneterepthalate (“PET”),polyphenylenesulfide (“PPS”), polyallylate, polyimide (“PI”),polycarbonate (“PC”), cellulosetriacetate (“CAT”), cellulose acetatepropionate (“CAP”), or a combination thereof, for example. In anotherexemplary embodiment, the first substrate 110 may be a flexiblesubstrate including P1.

A plurality of pixel electrodes 120 may be disposed on the firstsubstrate 110. Although not illustrated in the drawing, a plurality ofcomponents may be further disposed between the first substrate 110 andthe plurality of pixel electrodes 120. In an exemplary embodiment, theplurality of components may include a buffer layer, a plurality ofconductive interconnections, an insulating layer, a plurality of thinfilm transistors (“TFTs”), and the like. In an exemplary embodiment, inthe plurality of TFTs, amorphous silicon, polysilicon, low-temperaturepolysilicon (“LTPS”), an oxide semiconductor, an organic semiconductor,or the like may be used as a channel layer. Types of channel layers ofthe plurality of TFTs may be different from each other. In an exemplaryembodiment, both of a TFT including an oxide semiconductor and a TFTincluding LTPS may be included in a single pixel unit in considerationof a role or a process sequence of a TFT.

The plurality of pixel electrodes 120, a pixel definition film 130, anda plurality of OLEDs 140 will be described on the basis of a first pixelelectrode 121 and a first OLED 141 with reference to FIGS. 1A and 2.

FIG. 2 shows plan and cross-sectional views illustrating a first pixelunit illustrated in FIG. 1A.

Referring to FIGS. 1A and 2, in an exemplary embodiment, the first pixelelectrode 121 may be an anode electrode. When the first pixel electrode121 is an anode electrode, the first pixel electrode 121 may be providedwith a transparent electrode or semitransparent electrode, or include areflective material such as aluminum, silver, chromium, or an alloythereof. In an exemplary embodiment, the transparent or translucentelectrode may include at least one of indium tin oxide (“ITO”), indiumzinc oxide (“IZO”), zinc oxide (ZnO), indium oxide (In₂O₃), indiumgallium oxide (“IGO”), and aluminum zinc oxide (“AZO”), for example. Inan exemplary embodiment, the reflective material may include at leastone reflective film including silver (Ag), magnesium (Mg), chromium(Cr), gold (Au), platinum (Pt), nickel (Ni), copper (Cu), tungsten (W),and aluminum (Al), for example.

The pixel definition film 130 may be disposed on the first pixelelectrode 121. An opening OP1 which exposes at least a portion of thefirst pixel electrode 121 is defined in the pixel definition film 130.The pixel definition film 130 may include an organic material or aninorganic material. In an exemplary embodiment, the pixel definitionfilm 130 may include a material such as a photoresist, a polyimideresin, an acrylic resin, a silicon compound, a polyacrylic resin, or thelike.

In an exemplary embodiment, the first pixel electrode 121 may have adiamond shape. In an exemplary embodiment, the opening OP1 of the pixeldefinition film 130 may also have a diamond shape. However, the shape ofthe first pixel electrode 121 and the shape of the opening OP1 of thepixel definition film 130 are not limited to those illustrated in FIG.1A. That is, the shape of the first pixel electrode 121 and the shape ofthe opening OP1 of the pixel definition film 130 may vary according toan arrangement structure of a plurality of pixel units.

The plurality of OLEDs 140 may be disposed on the plurality of pixelelectrodes 120 and the pixel definition film 130. The plurality of OLEDs140 will be described on the basis of the first OLED 141. The first OLED141 may be disposed in a region of the first pixel electrode 121, whichis exposed through the opening OP1 of the pixel definition film 130.That is, the first OLED 141 may overlap the opening OP1 of the pixeldefinition film 130. In an exemplary embodiment, the first OLED 141 maycover at least a portion of the opening OP1 of the pixel definition film130.

In an exemplary embodiment, the first OLED 141 may emit one of redlight, green light, and blue light, for example. In an exemplaryembodiment, a wavelength of the red light may range from about 620nanometers (nm) to about 750 nm, and a wavelength of the green light mayrange from about 495 nm to about 570 nm, for example. Also, a wavelengthof the blue light may range from about 450 nm to about 495 nm, forexample. However, the invention is not limited thereto, and the firstOLED may emit various other color lights.

In another exemplary embodiment, the first OLED 141 may emit whitelight, for example. In an exemplary embodiment, when the first OLED 141may emit white light, the first OLED 141 may have a structure in which ared light-emitting layer, a green light-emitting layer, and a bluelight-emitting layer are stacked, for example. The first OLED 141 mayfurther include a separate color filter for displaying red, green, orblue, for example.

Although not illustrated in the drawings, the first OLED 141 may have amultilayer structure including a hole injection layer (“HIL”), a holetransport layer (“HTL”), an electron transport layer (“ETL”), anelectron injection layer (“EIL”), and the like, for example.

Referring back to FIG. 1A, a common electrode 150 may be disposed on thefirst OLED 141 and the pixel definition film 130. In an exemplaryembodiment, the common electrode 150 may be disposed on entire surfacesof the first OLED 141 and the pixel definition film 130. In an exemplaryembodiment, the common electrode 150 may be a cathode electrode. In anexemplary embodiment, the common electrode 150 may include at least oneof Li, Ca, LiF/Ca, LiF/AI, Al, Ag, and Mg, for example. Also, the commonelectrode 150 may be provided with a metal thin film having a low workfunction. In an exemplary embodiment, the common electrode 150 may be atransparent or translucent electrode including at least one of ITO, IZO,ZnO, indium oxide (In₂O₃), IGO, and AZO.

A first buffer layer 160 may be disposed on the common electrode 150.There are no specific limitations on a material of the first bufferlayer 160. In an exemplary embodiment, the first buffer layer 160 mayinclude an inorganic material or an organic material. In an alternativeexemplary embodiment, the first buffer layer 160 may have a structure inwhich at least one of an organic layer and an inorganic layer form asingle layer or are stacked in a multilayer, for example. In anotherexemplary embodiment, the first buffer layer 160 may be an air layer. Inanother exemplary embodiment, the first buffer layer 160 may be omitted.

Although not illustrated in the drawings, a capping layer may bedisposed on the common electrode 150. The capping layer may preventlight incident on the common electrode 150 from being lost by totalreflection. In an exemplary embodiment, the capping layer may beprovided with an organic film or an inorganic film. In an exemplaryembodiment, the first buffer layer 160 may serve as the capping layer.

A first encapsulation layer 170 may be disposed on the first substrate110 to cover the plurality of OLEDs 140. That is, the plurality of OLEDs140 may be disposed between the first substrate 110 and the firstencapsulation layer 170. The first encapsulation layer 170 may blockexternal oxygen and moisture from the plurality of OLEDs 140.

In an exemplary embodiment, the first encapsulation layer 170 may be atransparent insulating substrate. In an exemplary embodiment, the firstencapsulation layer 170 may be a glass substrate, a quartz substrate, atransparent resin substrate, or the like, for example. A sealing membermay be disposed between the first encapsulation layer 170 and the firstsubstrate 110 to bond the first encapsulation layer 170 and the firstsubstrate 110.

The diffraction panel 200 may be disposed on the display panel 100. Morespecifically, the diffraction panel 200 may be disposed on a path oflight emitted from the plurality of OLEDs 140 included in the displaypanel 100.

In an exemplary embodiment, the diffraction panel 200 may be coupled tothe display panel 100 through a first adhesive member 310. Here, in anexemplary embodiment, the first adhesive member 310 may be apressure-sensitive adhesive (“PSA”) member. However, the invention isnot limited thereto, and in another exemplary embodiment, the firstadhesive member 310 may be an optically clear adhesive (“OCA”) member.In an alternative exemplary embodiment, the first adhesive member 310may be an optically clear resin (“OCR”) film, for example. When thediffraction panel 200 is directly disposed on the display panel 100 anddoes not include a base layer, the diffraction panel 200 may be referredto as a diffraction layer. When the diffraction panel 200 is replaced bya diffraction layer, the first adhesive member 310 may be omitted.

The diffraction panel 200 may include a plurality of diffractionpatterns 210, a base layer 220, and a protective layer 230.

The plurality of diffraction patterns 210 may be disposed on the baselayer 220. That is, the base layer 220 may provide a base surface forthe plurality of diffraction patterns 210. There are no specificlimitations on a material of the base layer 220. In an exemplaryembodiment, the base layer 220 may include an organic material or aninorganic material.

The plurality of diffraction patterns 210 may be provided to protrude inan upward direction (on the basis of FIG. 1) of the base layer 220.Here, the upward direction of the base layer 220 is defined as adirection of the path of the light emitted from the plurality of OLEDs140.

The plurality of diffraction patterns 210 may diffract light emittedfrom the display panel 100 to enlarge an effective light emission area.Here, diffraction does not occur only in light provided to the pluralityof diffraction patterns 210. That is, the diffraction of the light maybe caused by a phenomenon of interference between light provided to theplurality of diffraction patterns 210 and light provided to a regionlocated between each of the plurality of diffraction patterns 210.However, for convenience of description, the patterns which are providedto protrude in the upward direction of the base layer 220 are defined asthe plurality of diffraction patterns 210, and a diffraction phenomenonof the light will be described on the basis of the plurality ofdiffraction patterns 210. A definition of the effective light emissionarea and an enlargement of the effective light emission area will bedescribed below.

Each of the plurality of diffraction patterns 210 may include first tothird refractive layers which are sequentially stacked. The plurality ofdiffraction patterns 210 will be described on the basis of a firstdiffraction pattern 211. Here, the first diffraction pattern 211 isarbitrarily selected from the plurality of diffraction patterns 210 todescribe the plurality of diffraction patterns 210. A location of thefirst diffraction pattern 211 in the plurality of diffraction patterns210 is not limited to that illustrated in FIG. 1A.

Referring to FIG. 1B, the first diffraction pattern 211 may include afirst refractive layer 211 a, a second refractive layer 211 b, and athird refractive layer 211 c. In an exemplary embodiment, the firstdiffraction pattern 211 may have a structure in which the firstrefractive layer 211 a, the second refractive layer 211 b, and the thirdrefractive layer 211 c are sequentially stacked. That is, the firstrefractive layer 211 a may be directly disposed on the base layer 220,and the second refractive layer 211 b may be located between the firstrefractive layer 211 a and the third refractive layer 211 c.

A refractive index of the first refractive layer 211 a may be determinedby a refractive index of the base layer 220 and a refractive index ofthe second refractive layer 211 b. A refractive index of the thirdrefractive layer 211 c may be determined by a refractive index of theprotective layer 230 and the refractive index of the second refractivelayer 211 b. A thickness t1 of the first refractive layer 211 a may bedetermined by the refractive index of the first refractive layer 211 a.A thickness t3 of the third refractive layer 211 c may be determined bythe refractive index of the third refractive layer 211 c.

More specifically, the refractive index and the thickness t1 of thefirst refractive layer 211 a and the refractive index and the thicknesst3 of the third refractive layer 211 c may be determined such thatreflectance of the first diffraction pattern 211 are sufficientlyreduced, and may be determined in consideration of refractive indexes orthicknesses of other components, for example, the second refractivelayer 211 b, the base layer 220, and the protective layer 230. Here, thereflectance of the first diffraction pattern 211 is defined as a ratioof an amount of light which is reflected by the first diffractionpattern 211 and provided back to the outside when it is assumed that anamount of light incident from the outside (hereinafter, referred to asexternal light) is 100.

In an alternative exemplary embodiment, first, the refractive index andthe thickness t1 of the first refractive layer 211 a and the refractiveindex and the thickness t3 of the third refractive layer 211 c may bedetermined, and accordingly, refractive indexes of the base layer 220and the protective layer 230 may be determined, for example. However, inconsideration of process conditions and a relationship between thediffraction panel 200 and other components, the refractive indexes andthe thicknesses t1 and t3 of the first refractive layer 211 a and thethird refractive layer 211 c may be easily determined according to therefractive indexes of the base layer 220 and the protective layer 230.

The refractive indexes and thicknesses t1 to t3 of the first to thirdrefractive layers 211 a to 211 c may vary according to the reflectanceof the first diffraction pattern 211. In other words, the reflectance ofthe plurality of diffraction patterns 210 including the firstdiffraction pattern 211 may be controlled by adjusting at least one ofthe refractive index and the thickness of the diffraction pattern. Thiswill be described below with reference to FIG. 8.

The sum of the thicknesses t1 to t3 of the first to third refractivelayer 211 a to 211 c may be expressed as a first thickness T1, forexample. The first thickness T1 is defined as the shortest distance froma lower surface of the first diffraction pattern 211 to an upper surfacethereof.

The protective layer 230 may be disposed on the plurality of diffractionpatterns 210. In an exemplary embodiment, the protective layer 230 maybe provided to cover the plurality of diffraction patterns 210. Thereare no specific limitations on a material of the protective layer 230.In an exemplary embodiment, the protective layer 230 may be providedwith an organic film or an inorganic film. In an exemplary embodiment,the organic film may include at least one of an acrylic resin, amethacrylic resin, a polyisoprene resin, a vinyl resin, an epoxy resin,a urethane resin, a cellulose resin, a siloxane resin, a polyimideresin, a polyamide resin, and a perylene resin, for example. In anexemplary embodiment, the inorganic film may include at least one ofaluminum oxide, titanium oxide, silicon oxide, silicon oxynitride,zirconium oxide, and hafnium oxide, for example.

In another exemplary embodiment, the protective layer 230 may include anadhesive material for bonding with a component disposed on thediffraction panel 200. Here, there are no specific limitations on a typeof the adhesive material. In an exemplary embodiment, when theprotective layer 230 includes an adhesive material, the protective layer230 may be a PSA layer or an OCA layer. Accordingly, a separate adhesivemember may not be disposed between the protective layer 230 and thecomponent which is disposed on the diffraction panel 200.

Next, shapes of the plurality of diffraction patterns 210 will bedescribed with reference to FIGS. 3A and 4.

FIG. 3A is a perspective view illustrating the base layer and theplurality of diffraction patterns illustrated in FIG. 1A. FIG. 4 is aplan view illustrating the base layer and the plurality of diffractionpatterns illustrated in FIG. 1A. FIG. 5 is a cross-sectional view takenalong line 12-12′ illustrated in FIG. 4. FIG. 6 is a cross-sectionalview taken along a first imaginary line illustrated in FIG. 5. Forconvenience of description, the protective layer 230 will be omitted inFIGS. 3A to 6.

First, the shapes and the number of the plurality of diffractionpatterns 210 will be described.

Referring to FIGS. 3A and 4, in an exemplary embodiment, the pluralityof diffraction patterns 210 may have a cylindrical shape. That is,shapes of upper surfaces and lower surfaces of the plurality ofdiffraction patterns 210 may be a circular shape. Here, the circularshape includes a circular shape and a shape similar to a circle inconsideration of process conditions and the like when viewed from thetop. In an exemplary embodiment, the shape similar to a circle mayinclude an elliptical shape or a polygonal shape that is substantiallysimilar to a circle, for example. However, the shapes of the pluralityof diffraction patterns 210 are not limited to those illustrated in FIG.3A. Another exemplary embodiment of the shapes of the plurality ofdiffraction patterns 210 will be described below.

In an exemplary embodiment, the number of diffraction patterns disposedin a first direction X and the number of diffraction patterns disposedin a second direction Y may be the same. However, the invention is notlimited thereto, and the numbers of the diffraction patterns disposed ineach of the directions may be different.

Next, periodicity of the plurality of diffraction patterns 210 will bedescribed with reference to FIGS. 3A to 6.

The periodicity of the plurality of diffraction patterns 210 will bedescribed on the basis of the first diffraction pattern 211 and thesecond diffraction pattern 212. Here, the second diffraction pattern 212may be adjacent to the first diffraction pattern 211 in the firstdirection X and may include a first refractive layer 212 a, a secondrefractive layer 212 b, and a third refractive layer 212 c. Here, thefirst direction X is defined as a row direction with reference to FIG.3A. The second direction Y is defined as a column directionperpendicular to the first direction X.

The first diffraction pattern 211 and the second diffraction pattern 212may be disposed to have a first period DP1. Here, the first period DP1is defined on the basis of a cross section of the diffraction pattern.

The periodicity will be described in more detail. A cross section 211 b1 of the first diffraction pattern 211 is defined as a surface takenalong a first imaginary line cl1. Here, the first imaginary line cl1 isdefined as a line passing through a halfway point of the first thicknessT1 of the first diffraction pattern 211. Accordingly, the firstimaginary line cl1 passes through the second refractive layer 211 b ofthe first diffraction pattern 211. As a result, the cross section 211 b1 of the first diffraction pattern 211 refers to a cross section of thesecond refractive layer 211 b. Similarly, a cross section 212 b 1 of thesecond diffraction pattern 212 refers to a cross section of the secondrefractive layer 212 b. That is, the first period DP1 is defined as adistance from one side of the cross section 211 b 1 of the firstdiffraction pattern 211 to one side of the cross section 212 b 1 of thesecond diffraction pattern 212. In an exemplary embodiment, the firstperiod DP1 may range from about 6.5 micrometers (μm) to about 7.5 μm,for example.

The first diffraction pattern 211 may have a first length d1 in a planecs1 cut by the first imaginary line cl1. Here, the first length d1 isalso defined on the basis of the cross section of the diffractionpattern. That is, the first length d1 refers to a width of the crosssection 211 b 1 of the first diffraction pattern 211. In an exemplaryembodiment, the first length d1 may range from about 1.5 μm to about 2.5μm, for example.

In FIG. 5, the first imaginary line cl1 is illustrated as passingthrough the second refractive layer 211 b of the first diffractionpattern 211, but the invention is not limited thereto. That is, when thethicknesses t1 to t3 of the first to third refractive layer 211 a to 211c are changed in consideration of the reflectance of the plurality ofdiffraction patterns 210 including the first diffraction pattern 211,the first imaginary line cl1 may pass through the first refractive layer211 a or the third refractive layer 211 c.

Referring back to FIGS. 3A and 4, a period between the diffractionpatterns, which are disposed in the first direction X, among theplurality of diffraction patterns 210 may be the first period DP1.Although not illustrated in the drawings, in an exemplary embodiment, aperiod between the diffraction patterns disposed in the second directionY may also be the first period DP1. However, the invention is notlimited thereto, and the period between the diffraction patternsdisposed in the first direction X and the period between the diffractionpatterns disposed in the second direction Y may be different.

Hereinafter, the definition of the effective light emission area and theenlargement of the effective light emission area will be described withreference to FIGS. 7A to 7C.

FIGS. 7A to 7C are views for describing the enlargement of the effectivelight emission area of the display device according to an exemplaryembodiment of the invention. For convenience of description, theenlargement of the effective light emission area will be described onthe basis of the first pixel electrode 121 and the first OLED 141, whichare included in a first pixel unit PX1 described in FIG. 2.

A light emission pattern which is generated in a first region TA1 bylight L1 emitted from the first OLED 141 is defined as a first lightemission pattern EP1. A light emission pattern which is generated beforethe light L1 emitted from the first OLED 141 passes through thediffraction panel 200 may also be defined as the first light emissionpattern EP1. Also, a light emission pattern which is generated in asecond region TA2 by light L2 a, light L2 b, and light L2 c passingthrough the diffraction panel 200 is defined as a second light emissionpattern EP2. Hereinafter, the light L2 a, light L2 b, and light L2 cpassing through the diffraction panel 200 are referred to as diffractedlight. Here, the first region TA1 and the second region TA2 are assumedto have the same area.

The light L1 emitted from the first OLED 141 may pass through the firstencapsulation layer 170 to be provided to the diffraction panel 200. Apath of the light L1 emitted from the first OLED 141 may be changed tobe a predetermined angle by a phase difference in a refractive index ofthe first encapsulation layer 170. In this specification, a refractiveindex of the first buffer layer 160 will be ignored in consideration ofrelative thicknesses of the first buffer layer 160 and the firstencapsulation layer 170. Content of the change of the path of the lightdue to the refractive index of the first encapsulation layer 170 will bedescribed in a relationship with a first diffraction distance β1described below.

The diffraction panel 200 may diffract the light L1 emitted from thefirst OLED 141 to generate first diffracted light L2 a, seconddiffracted light L2 b, and third diffracted light L2 c. Each of thefirst diffracted light L2 a, the second diffracted light L2 b, and thethird diffracted L2 c may include zero-order diffracted light andfirst-order diffracted light. Here, the zero-order diffracted lightrefers to light having the same light path before and after beingdiffracted by the diffraction panel 200. Also, the first-orderdiffracted light refers to light having a path changed by thediffraction panel 200 and a diffraction angle θ on the basis of thezero-order diffracted light.

Referring to FIG. 7A, for example, each of reference numerals L2 b 1, L2a 1, and L2 c 1 is zero-order diffracted light. Also, each of referencenumerals L2 b 2, L2 b 3, L2 a 2, L2 a 3, L2 c 2, and L2 c 3 isfirst-order diffracted light. In another exemplary embodiment, the firstdiffracted light L2 a, the second diffracted light L2 b, and the thirddiffracted L2 c may further include second or more order diffractedlight. In this specification, examples of the first diffracted light L2a, the second diffracted light L2 b, and the third diffracted L2 c willbe described as including zero-order diffracted light and first-orderdiffracted light.

The first diffracted light L2 a, the second diffracted light L2 b, andthe third diffracted L2 c may include first effective light L2 a 1,second effective light L2 b 3, and third effective L2 c 2 having pathsperpendicular to the first substrate 110, respectively. Here, thedirection perpendicular to the first substrate 110 may include adirection substantially perpendicular to the first substrate 110 as wellas a direction totally perpendicular to the first substrate 110. Thereare no limitations on the order of the diffracted light as long aseffective light has a path perpendicular to the first substrate 110.That is, the effective light may include both zero-order diffractedlight and first-order diffracted light as long as the effective lighthas a path in a vertical direction.

The diffraction panel 200 may diffract the light L1 emitted from thefirst OLED 141 to generate the first effective light L2 a 1, the secondeffective light L2 b 3, and the third effective light L2 c 2. A lightemission pattern, which is generated in the second region TA2 by thefirst effective light L2 a 1, the second effective light L2 b 3, and thethird effective light L2 c 2, is defined as the second light emissionpattern EP2. The second light emission pattern EP2 may include areference light emission pattern Pref and a plurality of replicatedlight emission patterns P1 to P8 replicated from the reference lightemission pattern Pref. However, luminance of the reference lightemission pattern Pref and luminances of the plurality of replicatedlight emission patterns P1 to P8 may be different.

As described above, an area of the first region TA1 and an area of thesecond region TA2 are the same. The number of light emission patternsincluded in the second region TA2 is greater than the number of lightemission patterns included in the first region TA1. Accordingly, an areaof a light emission region of the second region TA2 is greater than anarea of a light emission region of the first region TA1. That is, aregion of the second region TA2 in which light is not emitted (i.e., anon-emission region) may be expressed as having a smaller area than thatof the first region TA1.

The light emission region having a large area may be expressed as alarge light emission area ratio. That is, the light emission area ratiois defined as a ratio of an area of light emission patterns existing inone region to an area of the region. Here, light emission patterns forcalculating a light emission area ratio may include all of a referencelight emission pattern and replicated light emission patterns. In anexemplary embodiment, the second region TA2 includes nine light emissionpatterns including the reference light emission pattern Pref and theplurality of replicated light emission patterns P1 to P8 while the firstregion TA1 includes one light emission pattern, for example.Accordingly, a light emission area ratio of the second region TA2 isgreater than a light emission area ratio of the first region TA1.

That is, the diffraction panel 200 may diffract the light L1 emittedfrom the first OLED 141 to generate a plurality of replicated lightemission patterns, and thus the light emission area thereof may beenlarged. Also, since the light emission area is increased, luminousefficiency of the light L1 emitted from the first OLED 141 may beimproved.

However, the luminance of the replicated light emission pattern may beused as a factor for calculating the light emission area ratio only whenthe luminance of the replicated light emission pattern is about 3% ormore of the luminance of the reference light emission pattern.Hereinafter, the sum of an area of the reference light emission patternand areas of the replicated light emission patterns which are replicatedfrom the reference light emission pattern and satisfy about 3% or moreof the luminance of the reference light emission pattern in one regionis defined as the effective light emission area. Also, a ratio of theeffective light emission area to an area in one region is defined as aneffective light emission area ratio. In an exemplary embodiment,replicated light emission patterns for calculating the effective lightemission area ratio may be limited to patterns having about 3% or moreof the luminance of the reference light emission pattern among thereplicated light emission patterns, for example. Accordingly, theluminance of the plurality of replicated light emission patterns P1 toP8 may be used as a factor for calculating the effective light emissionarea ratio when the luminances of the plurality of replicated lightemission patterns P1 to P8 are about 3% or more of the luminance of thereference light emission pattern Pref.

The luminance of the reference light emission pattern Pref and theluminances of the plurality of replicated light emission patterns P1 toP8 may be controlled by adjusting the first period DP1 of the pluralityof diffraction patterns 210, the first thickness T1 (refer to FIG. 5),and the first length d1 (refer to FIG. 6).

Here, the first thickness T1 is defined as the sum of the thicknesses t1to t3 of the first to third refractive layers 211 a to 211 c (refer toFIG. 5). As described above, the thicknesses t1 and t3 of the first andthird refractive layers 211 a and 211 c may be adjusted to sufficientlyreduce a reflectance of the diffraction panel 200. Therefore, first,conditions for reducing the reflectance of the diffraction panel 200will be described with reference to FIG. 8.

FIG. 8 is a view for describing a reduction of reflectance of lightincident on the first diffraction pattern illustrated in FIG. 1A. InFIG. 8, refraction of light incident on the protective layer 230 will beignored due to a difference between a refractive index of an externalcomponent of the protective layer 230 and the refractive index of theprotective layer 230.

First, a refractive index of each of the components will be described.

The refractive index of the first refractive layer 211 a and therefractive index of the third refractive layer 211 c are lower than therefractive index of the second refractive layer 211 b. There are nospecific limitations on values of the refractive indexes of the firstrefractive layer 211 a and the third refractive layer 211 c as long asthe refractive index of the first refractive layer 211 a and therefractive index of the third refractive layer 211 c are lower than therefractive index of the second refractive layer 211 b. In an alternativeexemplary embodiment, the refractive indexes of the first refractivelayer 211 a and the third refractive layer 211 c may be the same as ordifferent from each other as long as the refractive index of the firstrefractive layer 211 a and the refractive index of the third refractivelayer 211 c are lower than the refractive index of the second refractivelayer 211 b, for example. In an exemplary embodiment, the refractiveindexes of the first refractive layer 211 a and the third refractivelayer 211 c may be about 1.71, for example. In an exemplary embodiment,the refractive index of the second refractive layer 211 b may be about1.95, for example.

There are no specific limitations on materials of the first refractivelayer 211 a, the second refractive layer 211 b, and the third refractivelayer 211 c as long as the refractive index of the first refractivelayer 211 a and the refractive index of the third refractive layer 211 care lower than the refractive index of the second refractive layer 211b. In an exemplary embodiment, the materials of the first refractivelayer 211 a and the third refractive layer 211 c may be siliconoxynitride (SiON), for example. Also, in an exemplary embodiment, thematerial of the second refractive layer 211 b may be silicon nitride(SiN_(x)), for example.

The refractive indexes of the base layer 220 and the protective layer230 may be lower than the refractive indexes of the first refractivelayer 211 a and the third refractive layer 211 c. The refractive indexesof the base layer 220 and the protective layer 230 may be determinedaccording to a material capable of performing a function of eachcomponent. In an exemplary embodiment, the refractive indexes of thebase layer 220 and the protective layer 230 may be the same or differentas long as the refractive indexes of the protective layer 230 and thebase layer 220 are lower than the refractive indexes of the firstrefractive layer 211 a and the third refractive layer 211 c. In anexemplary embodiment, the refractive indexes of the base layer 220 andthe protective layer 230 may be about 1.5, for example.

Next, the thicknesses t1 to t3 of the first to third refractive layers211 a to 211 c will be described.

In an exemplary embodiment, the thickness t1 of the first refractivelayer 211 a and the thickness t3 of the third refractive layer 211 c maybe smaller than the thickness t2 of the second refractive layer 211 b.The thickness t1 of the first refractive layer 211 a and the thicknesst3 of the third refractive layer 211 c may be the same or different aslong as the thickness t1 of the first refractive layer 211 a and thethickness t3 of the third refractive layer 211 c are smaller than thethickness t2 of the second refractive layer 211 b. In an exemplaryembodiment, the thickness t1 of the first refractive layer 211 a and thethickness t3 of the third refractive layer 211 c may be about 800angstroms (Å), for example. Also, in an exemplary embodiment, thethickness t2 of the second refractive layer 211 b may be about 5,500 Å,for example.

Hereinafter, a reflection reducing effect of the first diffractionpattern 211 will be described in consideration of the refractive indexesand the thicknesses of the first to third refractive layers 211 a to 211c.

As described above, the thicknesses t1, t2, and t3 and the refractiveindexes of the first refractive layer 211 a, the second refractive layer211 b, and the third refractive layer 211 c may be adjusted tosufficiently reduce reflectance. More specifically, the thicknesses t1,t2, and t3 and the refractive indexes of the first refractive layer 211a, the second refractive layer 211 b, and the third refractive layer 211c may affect a length of a path of light incident on the thirdrefractive layer 211 c (hereinafter, referred to as an incident lightLa) to change a phase of the light. When phases of reflected beams oflight are different from each other, an attenuation effect due tooverlapping occurs when the reflected beams of light are combined, andamplitude of the reflected light is reduced. That is, the firstdiffraction pattern 211 may reduce the reflectance by reducing theamplitude of the reflected light using destructive interference of thelight.

As illustrated in FIG. 8, an incident light La, a first reflected lightLb, and a second reflected light Lc will be described as examples.

The incident light La is partially reflected at an interface (an uppersurface of the third refractive layer 211 c) between the protectivelayer 230 and the third refractive layer 211 c according to a differencebetween the refractive index of the protective layer 230 and therefractive index of the third refractive layer 211 c. The lightreflected at the upper surface of the third refractive layer 211 c willbe referred to as the first reflected light Lb.

A path of light transmitted through the third refractive layer 211 cwithout being reflected by the upper surface of the third refractivelayer 211 c is refracted by the difference between the refractive indexof the protective layer 230 and the refractive index of the thirdrefractive layer 211 c. The light with the refracted path is partiallyreflected at an interface (an upper surface of the second refractivelayer 211 b) between the third refractive layer 211 c and the secondrefractive layer 211 b according to a difference between the refractiveindex of the third refractive layer 211 c and the refractive index ofthe second refractive layer 211 b. The light reflected at the uppersurface of the second refractive layer 211 b will be referred to as thesecond reflected light Lc.

Here, a phase of the first reflected light Lb may be different from aphase of the second reflected light Lc. More specifically, the phase ofthe first reflected light Lb may be symmetrical with the phase of thesecond reflected light Lc, that is, may have a difference by 180degrees. Accordingly, when the first reflected light Lb and the secondreflected light Lc are recombined at the upper surface of the thirdrefractive layer 211 c, the first reflected light Lb and the secondreflected light Lc may destructively interfere with each other due to adifference between phases thereof. As a result, the amplitude of thereflected light may be reduced, which means that the reflectance of thefirst diffraction pattern 211 may be reduced.

That is, the refractive index and the thickness t3 of the thirdrefractive layer 211 c may be determined such that a condition forcausing the first reflected light Lb and the second reflected light Lcto destructively interfere with each other occurs. In other words, therefractive index and the thickness t3 of the third refractive layer 211c may be determined so that the phase of the first reflected light Lband the phase of the second reflected light Lc are different from eachother by 180 degrees.

In an exemplary embodiment, the refractive index of the third refractivelayer 211 c may satisfy the following Expression 1.n211c=√{square root over (n230*n211b)}  [Expression 1]

Here, n211 c denotes the refractive index of the third refractive layer211 c, and n230 denotes the refractive index of the protective layer230. Further, n211 b denotes the refractive index of the secondrefractive layer 211 b.

Further, in an exemplary embodiment, the thickness t3 of the thirdrefractive layer 211 c may satisfy the following Expression 2.t3=λ_(La)/(4*n211c)  [Expression 2]

Here, λ_(La) denotes a wavelength of the incident light La, and n211 cdenotes the refractive index of the third refractive layer 211 cdetermined by Expression 1.

The reflection reducing effect may be further improved in comparison toa multilayer structure in which layers having different refractiveindexes are stacked. Accordingly, the refractive index and the thicknesst1 of the first refractive layer 211 a may satisfy Expressions 3 and 4,respectively.n211a=√{square root over (n230*n211b)}  [Expression 3]t1=Δ_(211a)/(4*n211a)  [Expression 4]

In Expressions 3 and 4, n211 a denotes the refractive index of the firstrefractive layer 211 a and n220 denotes the refractive index of the baselayer 220. Further, λ_(211a) denotes a wavelength of light incident onthe first refractive layer 211 a. When the wavelength of the lightincident on the first refractive layer 211 a is the same as thewavelength of the incident light La, λ_(211a) may be replaced by λ_(La).

That is, the display device according to the exemplary embodiment of theinvention may adjust the refractive index and the thickness of therefractive layer of each of the plurality of diffraction patterns 210,and thus the amplitude of the light reflected by the plurality ofdiffraction patterns 210 may be reduced and the reflectance may bereduced through the destructive interference of the light.

The following Table 1 is for describing a degree of reflectancereduction.

TABLE 1 Single-layer Multilayer Structure Structure Degree of Increasein 2.35% 0.02% Reflectance

The single-layer structure in Table 1 is a case in which the firstrefractive layer 211 a and the third refractive layer 211 c are omittedfrom the first diffraction pattern 211 (however, the first thickness T1is the same). Further, the multilayer structure in Table 1 is a case inwhich the first diffraction pattern 211 includes the first refractivelayer 211 a and the third refractive layer 211 c according to anexemplary embodiment of the invention.

Table 1 illustrates a degree of increase in reflectance when each of thediffraction patterns is included. That is, referring to Table 1, it maybe seen that the multilayer structure having the first diffractionpattern 211 including the first refractive layer 211 a and the thirdrefractive layer 211 c has a lower degree of increase in reflectancethan the single-layer structure. It may be seen that this means that thereflectance may be reduced by about 2.33% relative to the single-layerstructure.

FIGS. 9A and 9B show graphs illustrating reflectance of an OLED displayaccording to an exemplary embodiment of the invention. FIG. 9Aillustrates reflectance of the single-layer structure of Table 1, andFIG. 9B illustrates reflectance of the multilayer structure of Table 1.

Referring to FIG. 9A, reflectance r1 of the single-layer structure ishigher than reflectance r2 of the multilayer structure of FIG. 9B.Specifically, it may be seen that the reflectance r2 of the multilayerstructure is lower than the reflectance r1 of the single-layer structurein a wavelength range (about 450 nm to about 750 nm) of the lightemitted from the plurality of OLEDs 140 (refer to FIG. 1A).

Next, factors for satisfying about 3% or more of the luminance of thereference light emission pattern Pref with the luminance of at least oneof the plurality of above-described replicated light emission patternsP1 to P8 will be described with reference to FIGS. 10(a) to 11(c).

FIG. 10(a) is a graph illustrating luminance according to a value ofd1/DP1 when an OLED emits blue light. FIG. 10(b) is a graph illustratingluminance according to a value of d1/DP1 when an OLED emits green light.FIG. 10(c) is a graph illustrating luminance according to a value ofd1/DP1 when an OLED emits red light. FIGS. 11(a) to 11(c) are graphsobtained by normalizing luminances of the first replicated lightemission pattern P1 and the fifth replicated light emission pattern P5on the basis of the luminance of the reference light emission patternPref, which are respectively illustrated in FIGS. 10(a) to 10(c).Intensity in each of FIGS. 10(a) to 11(c) refers to intensity of theluminance.

The first diffraction pattern 211 will be mainly described withreference to FIGS. 6, 7, 10, and 11. The luminance of the referencelight emission pattern Pref and the luminances of the plurality ofreplicated light emission patterns P1 to P8 may be determined by thefirst period DP1, the first length d1, the first thickness T1, therefractive indexes of the first to third refractive layers 211 a to 211c of the first diffraction pattern 211, and the refractive index of theprotective layer 230.

Here, when a relationship between the first period DP1 and the firstlength d1 satisfies Expression 5, which will be described below, and arelationship between the first thickness T1, the refractive indexes ofthe first to third refractive layers 211 a to 211 c of the firstdiffraction pattern 211, and the refractive index of the protectivelayer 230 satisfies Expression 6, which will be described below, theluminance of at least one light emission pattern of the plurality ofreplicated light emission patterns P1 to P8 may be about 3% or more ofthe luminance of the reference light emission pattern Pref.

In an exemplary embodiment, the first to fourth replicated lightemission patterns P1, P2, P3, and P4, which are disposed in the same rowor column as the reference light emission pattern Pref, among theplurality of replicated light emission patterns P1 to P8 may have thesame luminance. Also, in an exemplary embodiment, the fifth to eighthreplicated light emission patterns P5, P6, P7, and P8, which aredisposed in a diagonal direction to the reference light emission patternPref, among the plurality of replicated light emission patterns P1 to P8may have the same luminance. However, in an exemplary embodiment, thefirst to fourth replicated light emission patterns P1, P2, P3, and P4and the fifth to eighth replicated light emission patterns P5, P6, P7,and P8 may have different luminances. Hereinafter, the reference lightemission pattern Pref, the first replicated light emission pattern P1,and the fifth replicated light emission pattern P5 will be mainlydescribed.

First, the relationship between the first period DP1 and the firstlength d1 will be described with reference to Expression 5. The firstperiod DP1 and the first length d1 should satisfy the followingExpression 5.0.4≤d1/DP1≤1  [Expression 5]

Referring to FIGS. 10(a) to 11(c), it may be seen that when the value ofd1/DP1 increases, the luminance of the reference light emission patternPref substantially decreases and the luminances of the first replicatedlight emission pattern P1 and the fifth replicated light emissionpattern P5 substantially increase.

Also, referring to FIGS. 11(a) to 11(c) in which the luminances arenormalized on the basis of the reference light emission pattern Pref, itmay be seen that the luminance of the first replicated light emissionpattern P1 is about 3% or more of the luminance of the reference lightemission pattern Pref when the value of d1/DP1 is about 0.4 or more, forexample. When the value of d1/DP1 ranges from about 0.7 to about 0.9,the luminance of the first replicated light emission pattern P1 may behigher than the luminance of the reference light emission pattern Pref.

The case in which the value of d1/DP1 is 1 indicates that the firstperiod DP1 and the first length d1 are equal. However, since a crosssection of the first diffraction pattern 211 has circular shape, thecross section of the first diffraction pattern 211 has a region which isnot in contact with a cross section of an adjacent diffraction patterneven when the first period DP1 and the first length d1 are equal.Therefore, the value of d1/DP1 may include 1.

Next, the relationship between the first thickness T1 of the firstdiffraction pattern 211, the refractive indexes of the first to thirdrefractive layers 211 a to 211 c of the first diffraction pattern 211,and the refractive index of the protective layer 230 will be describedwith reference to Expression 6. The first thickness T1 of the firstdiffraction pattern 211, the refractive indexes of the first to thirdrefractive layers 211 a to 211 c of the first diffraction pattern 211,and the refractive index of the protective layer 230 may satisfy thefollowing Expression 6.(m*λ _(L1))−60 (nm)≤A≤(m*λ _(L1))+60 (nm)U=[{(n230−n211c)×t3}+[{(n230−n211b)×t2}+(n230−n211a)×t1)]A≠U  [Expression 6]

Here, λ_(L1) denotes a wavelength of the light L1 emitted from the firstOLED 141, and n230 denotes the refractive index of the protective layer230. Further, units of U and A are nm, and m is an integer equal to orgreater than 0.

The above feature will be described in more detail with reference toFIGS. 6, 7, 12, and 13.

FIG. 12(a) is a graph illustrating luminance according to a value of Uwhen an OLED emits blue light. FIG. 12(b) is a graph illustratingluminance according to a value of U when an OLED emits green light. FIG.12(c) is a graph illustrating luminance according to a value of U whenan OLED emits red light. FIGS. 13(a) to 13(c) are graphs obtained bynormalizing the luminances of the first replicated light emissionpattern P1 and the fifth replicated light emission pattern P5 on thebasis of the luminance of the reference light emission pattern Pref,which are illustrated in FIGS. 12(a) to 12(c).

Referring to FIGS. 12(a) to 12(c), the reference light emission patternPref is repeatedly increased or decreased as the value of U isincreased. The luminance of the reference light emission pattern Prefaccording to the value of U may have a substantially sinusoidal shape onthe graph.

Referring to FIGS. 13(a) to 13(c) in which the luminances are normalizedon the basis of the reference light emission pattern Pref, theluminances of the first replicated light emission pattern P1 and thefifth replicated light emission pattern P5 are repeatedly increased ordecreased as the value of U is increased. That is, the luminances of thefirst replicated light emission pattern P1 and the fifth replicatedlight emission pattern P5 according to the value of U may have asubstantially sinusoidal shape on the graph.

Hereinafter, a description will be given with reference to FIG. 13(c).Sections m1 to m3 illustrated in FIG. 13(c) are regions in which both ofthe luminances of the first replicated light emission pattern P1 and thefifth replicated light emission pattern P5 are less than about 3% of theluminance of the reference light emission pattern Pref. That is, thesections m1 to m3 are included in a range of A of Expression 6.Therefore, a range of the value of U corresponds to the remaining rangeexcept the range of A of Expression 6. In an exemplary embodiment, thesection m2 of FIG. 13(c) is a section illustrating a range of a value ofA when (m=1), for example. Since λ_(L1) is 620 nm in FIG. 13(c), whenλ_(L1) is applied to Expression 6, the above values may be expressed asfollows.(1*620 nm)−60 (nm)≤A≤(1*620 nm)+60 (nm)=>560 nm≤λ≤680 nm

Referring to FIG. 13(c), it may be seen that both of the luminances ofthe first replicated light emission pattern P1 and the fifth replicatedlight emission pattern P5 are less than about 3% of the luminance of thereference light emission pattern Pref in the range of the value of A(560 n≤A≤680 nm).

Accordingly, when the value of U corresponds to the remaining rangeexcept the range of A of Expression 6, at least one of the firstreplicated light emission pattern P1 and the fifth replicated lightemission pattern P5 may satisfy about 3% or more of the luminance of thereference light emission pattern Pref.

As a result, in the plurality of diffraction patterns 210, when therelationship between the first period DP1 and the first length d1satisfies Expression 5 and the relationship between the first thicknessT1 of the first diffraction pattern 211, the refractive indexes of thefirst to third refractive layers 211 a to 211 c of the first diffractionpattern 211, and the refractive index of the protective layer 230satisfies Expression 6, the luminance of at least one light emissionpattern of the plurality of replicated light emission patterns P1 to P8may be about 3% or more of the luminance of the reference light emissionpattern Pref.

However, there are no specific limitations on the ranges of the firstperiod DP1 and the first length d1 as long as the relationship betweenthe first period DP1 and the first length d1 satisfies Expression 5. Inan exemplary embodiment, the first period DP1 may range from about 3.5μm to about 20 μm, for example. In this case, the first length d1 mayrange from about 1.4 μm to about 20 μm, for example.

Also, there are no limitations on the value of U as long as therelationship between the first thickness T1 of the first diffractionpattern 211, the refractive indexes of the first to third refractivelayers 211 a to 211 c of the first diffraction pattern 211, and therefractive index of the protective layer 230 satisfies Expression 6.

Referring to FIG. 10, when the value of d1/DP1 ranges from 0.45 to 1,both of the luminances of the first replicated light emission pattern P1and the fifth replicated light emission pattern P5 may be about 3% ormore of the luminance of the reference light emission pattern Pref. Thatis, when the value of d1/DP1 satisfies the range of 0.45 to 1 and thevalue of U satisfies the range of Expression 6, both of the luminancesof the first replicated light emission pattern P1 and the fifthreplicated light emission pattern P5 may be about 3% or more of theluminance of the reference light emission pattern Pref. This means thatall of the luminances of the plurality of replicated light emissionpatterns P1 to P8 may be about 3% or more of the luminance of thereference light emission pattern Pref.

FIG. 14 shows views for describing an enlargement of an effective lightemission area of light emitted from an OLED which emits red light in thedisplay device according to an exemplary embodiment of the invention.

FIG. 14(a) is a view illustrating a plurality of first light emissionregions TA1R. FIG. 14(b) is a view illustrating a plurality of secondlight emission regions TAR2. Here, the first light emission region TA1Ris defined as a region in which a light emission pattern generated by anOLED, which emits red light, of the plurality of OLEDs 140 is disposed.Also, the second light emission region TA2R is defined as a region inwhich light emitted from the OLED which emits red light is diffracted bythe diffraction panel 200 so that the generated light emission patternis disposed.

Referring to FIGS. 14(a) and 14(b), it may be seen that the number oflight emission patterns disposed in the first light emission region TA1Ris smaller than the number of light emission patterns disposed in thesecond light emission region TA2R. That is, the diffraction panel 200may diffract the light emitted from the plurality of OLEDs 140 so thatthe effective light emission area may be enlarged.

FIG. 15 shows views for describing an enlargement of an effective lightemission area of light emitted from an OLED which emits green light inthe display device according to an exemplary embodiment of theinvention. FIG. 16 shows views for describing enlargement of aneffective light emission area of light emitted from an OLED which emitsblue light in the display device according to an exemplary embodiment ofthe invention. However, a description identical to that given in FIG. 14will be omitted.

FIG. 15(a) is a view illustrating a plurality of first light emissionregions TA1G in which light emission patterns generated by OLEDs whichdisplay green are disposed. FIG. 15(b) is a view illustrating aplurality of second light emission regions TA2G in which light emissionpatterns generated by diffraction of light emitted from OLEDs whichdisplay green are disposed. Further, FIG. 16(a) is a view illustrating aplurality of first light emission regions TA1B in which light emissionpatterns generated by OLEDs which display blue are disposed. FIG. 16(b)is a view illustrating a plurality of second light emission regions TA2Bin which light emission patterns generated by diffraction of lightemitted from OLEDs which display blue are disposed.

Referring to FIGS. 7A and 14 to 16, the light emitted from the firstOLED 141 is diffracted by the diffraction panel 200. As described above,the effective light emission area is increased by the plurality ofreplicated light emission patterns P1 to P8 which are replicated andgenerated from the reference light emission pattern Pref by thediffraction. However, referring to FIGS. 14(b), 15(b), and 16(b),distances between the light emission patterns are different. As aresult, it may be seen that a first diffraction distance β1 defined asthe shortest distance between the reference light emission pattern Prefand one of the plurality of replicated light emission patterns P1 to P8is different for each light emission color.

That is, the first diffraction distance β1 may vary according to thelight emission color of the OLED. Also, the first diffraction distanceβ1 may vary according to a distance Z (refer to FIG. 17) between thediffraction panel 200 and the plurality of OLEDs 140, refractive indexesof components disposed between the diffraction panel 200 and theplurality of OLEDs 140, and the like in addition to the light emissioncolor.

Referring to the following Table 2, the first diffraction distance β1may affect the above-described effective light emission area ratio. Morespecifically, it may be seen that the effective light emission arearatio is substantially increased as the first diffraction distance β1 isincreased. That is, the effective light emission area ratio may becontrolled by adjusting factors that affect the first diffractiondistance β1.

TABLE 2 Effective Light Emission Area Ratio (%) β1 (μm) Red (R) Green(G) Blue (B) 0.0 5.8 6.6 6.9 2.4 13.4 19.1 14.8 4.8 19.5 32.1 27.7 7.224.7 48.6 39.0 9.6 47.8 82.6 61.1 12.1 74.4 93.9 83.8 14.5 77.1 86.689.0 16.9 79.5 97.9 93.8 19.3 89.1 85.6 96.5

Hereinafter, the factors that affect the first diffraction distance β1,which affects the effective light emission area ratio, will be describedwith reference to FIG. 17.

FIG. 17 is a view for describing the factors that affect the firstdiffraction distance. However, a description identical to that given inFIG. 7A will be omitted.

Referring to FIG. 17, the first diffraction distance β1 may bedetermined by the light emission color of the first OLED 141, thedistance Z between the diffraction panel 200 and the plurality of OLEDs140, the refractive index of the first buffer layer 160, the refractiveindex of the first encapsulation layer 170, the refractive index of thebase layer 220, the first period DP1 (refer to FIG. 6) of the pluralityof diffraction patterns 210, and the like.

The first diffraction distance β1 may be expressed by the followingExpression 7. However, refractive indexes of the first adhesive member310 and the common electrode 150, which have a relatively smallthickness, will be ignored.

$\begin{matrix}{{\beta 1} = {{z\;{1 \cdot {\tan\left\lbrack {\sin^{- 1}\left( {\frac{\lambda 141}{D\; P\; 1} \cdot \frac{1}{n160}} \right)} \right\rbrack}}} + {z\;{2 \cdot {\tan\left\lbrack {\sin^{- 1}\left( {\frac{\lambda 141}{DP1} \cdot \frac{1}{n170}} \right)} \right\rbrack}}} + {z\;{3 \cdot {\tan\left\lbrack {\sin^{- 1}\left( {\frac{\lambda\; 141}{DP1} \cdot \frac{1}{n\; 220}} \right)} \right\rbrack}}}}} & \left\lbrack {{Expression}\mspace{14mu} 7} \right\rbrack\end{matrix}$

Here, λ141 denotes a wavelength of the light emission color of the firstOLED 141. z1 denotes the shortest distance between the first OLED 141and the first encapsulation layer 170, and z2 denotes the shortestdistance between a lower surface of the first encapsulation layer 170and the base layer 220. Further, z3 denotes the shortest distancebetween a lower surface of the base layer 220 and the plurality ofdiffraction patterns 210. When the first buffer layer 160 is replaced byan air layer, n160 in Expression 7 may be replaced by a refractive index(about 1) of the air layer.

That is, the first diffraction distance β1 may be controlled byadjusting the light emission color of the first OLED 141, the distance Zbetween the diffraction panel 200 and the plurality of OLEDs 140, therefractive index of the first buffer layer 160, the refractive index ofthe first encapsulation layer 170, the refractive index of the baselayer 220, and the first period DP1 of the plurality of diffractionpatterns 210. The effective light emission area ratio may be increasedby adjusting the first diffraction distance β1.

However, when the first diffraction distance β1 is increased, blurringmay occur. Blurring refers to an image blurring phenomenon that may becaused by display colors of adjacent pixel units overlapping each other.Therefore, in order to balance between the increase of the effectivelight emission area ratio and the blurring, it is desired to calculatean appropriate first diffraction distance β1.

Each of the effective light emission area ratio and the blurring may beinfluenced by a distance between pixels. In an exemplary embodiment,even when two OLED displays in which arrangements of pixels aredifferent have the same diffraction distance, distances between adjacentpixel units may be different because arrangements of the pixel units aredifferent, for example. Accordingly, the two OLED displays may havedifferent effective light emission area ratios and degrees of occurrenceof blurring. That is, in order to balance between the effective lightemission area ratio and the blurring, it is necessary to consider thedistance between adjacent pixels as well as the first diffractiondistance β1.

First, a distance PP1 between pixels will be defined with reference toFIG. 18.

FIG. 18 is a plan view illustrating a pixel arrangement of the pluralityof pixel units included in the display panel illustrated in FIG. 1A.Although a first pixel unit PX1 is illustrated for describing the pixelarrangement structure in FIG. 18, the first pixel unit PX1 illustratedin FIG. 2 and the first pixel unit PX1 illustrated in FIG. 18 do nothave the same configuration.

An arrangement relationship between first to fourth pixel units PX1 toPX4 will be described with reference to FIG. 18. The first pixel unitPX1 may be disposed to be adjacent to the third pixel unit PX3 in thefirst direction X. The second pixel unit PX2 may be disposed to beadjacent to the fourth pixel unit PX4 in the first direction X. Thefirst pixel unit PX1 may be disposed to be adjacent to the second pixelunit PX2 in a diagonal direction with respect to the first direction Xand the second direction Y. The third pixel unit PX3 may be disposed tobe adjacent to the fourth pixel unit PX4 in a diagonal direction withrespect to the first direction X and the second direction Y. That is, inan exemplary embodiment, the first to fourth pixel units PX1 to PX4 maybe disposed in a parallelogram shape.

In an exemplary embodiment, although all of the first to fourth pixelunits PX1 to PX4 are illustrated in a diamond shape, shapes and sizes ofthe pixel units are not limited to those illustrated in FIG. 18.

In an exemplary embodiment, the first pixel unit PX1 may display red,for example. That is, the first pixel unit PX1 may include a red organiclight-emitting layer which emits red light, for example. In an exemplaryembodiment, the second and fourth pixel units PX2 and PX4 may displaygreen, for example. That is, each of the second and fourth pixel unitsPX2 and PX4 may include a green organic light-emitting layer which emitsgreen light, for example. In an exemplary embodiment, the third pixelunit PX3 may display blue, for example. That is, the third pixel unitPX3 may include a blue organic light-emitting layer which emits bluelight, for example.

The first to fourth pixel units PX1 to PX4 may constitute one pixelunit. That is, the first to fourth pixel units PX1 to PX4 may bedisposed in a pixel region DA1 in an RGBG PenTile manner. However, anarrangement relationship of the plurality of pixel units disposed in thepixel region DA1 is not limited to that illustrated in FIG. 18. In anexemplary embodiment, the arrangement relationship of the plurality ofpixel units may vary according to display colors of the pixel units, anapplied resolution and aperture ratio of the OLED display, and the like,for example.

Here, the distance PP1 between pixels is defined as a distance betweenpixel units which display the same color. More specifically, thedistance PP1 between pixels is defined as the distance between centerpoints of pixel electrodes each included in the pixel units whichdisplay the same color. Hereinafter, the second pixel unit PX2 and thefourth pixel unit PX4 which emit green light will be described asexamples.

In an exemplary embodiment, the distance PP1 between pixels may refer toa shortest distance between a first center point cp1 located in thesecond pixel unit PX2 and a second center point cp2 located in thefourth pixel unit PX4, for example. The first center point cp1 and thesecond center point cp2 are defined as center points of pixel electrodesincluded in the second pixel unit PX2 and the fourth pixel unit PX4,respectively.

The relationship between the first diffraction distance β1, the distancePP1 between pixels, and the effective light emission area ratio will bedescribed again. The following Table 3 illustrates an effective lightemission area ratio according to a value obtained by dividing the firstdiffraction distance β1 by the distance PP1 between pixels.

TABLE 3 Effective Light Emission Area Ratio (%) β1/PP1 Red (R) Green (G)Blue (B) 0.00 5.8 6.6 6.9 0.05 13.4 19.1 14.8 0.10 19.5 32.1 27.7 0.1524.7 48.6 39.0 0.21 47.8 82.6 61.1 0.26 74.4 93.9 83.8 0.31 77.1 86.689.0 0.36 79.5 97.9 93.8 0.41 89.1 85.6 96.5

Referring to Table 3, the effective light emission area ratio may besubstantially increased as the value obtained by dividing the firstdiffraction distance β1 by the distance PP1 between pixels is increased.

Next, the relationship between the first diffraction distance β1, thedistance PP1 between pixels, and blurring will be described withreference to Table 4. The following Table 4 illustrates a blurringrecognition score according to the value obtained by dividing the firstdiffraction distance β1 by the distance PP1 between pixels. Here, theblurring recognition score is a result of experimenting with a degree ofblurring recognition of the users while changing the value obtained bydividing the first diffraction distance β1 by the distance PP1 betweenpixels, and illustrates an average value of the degrees of blurringrecognition of the users. Here, when the visual blurring recognitionscore is 5 or more, blurring is recognized to an extent which may causethe users to feel discomfort when viewing the screen.

TABLE 4 Blurring Recognition Score β1/PP1 (Perfect score: 10 points) 0.21.3 0.45 1.2 0.89 2.4 1.33 4.0 1.89 5.1 2.26 6.4

Referring to Table 4, when the value obtained by dividing the firstdiffraction distance β1 by the distance PP1 between pixels is about 1.89or more, the blurring recognition score of the users is 5 or more. Thismeans that when the value obtained by dividing the first diffractiondistance β1 by the distance PP1 between pixels is greater than about1.9, most users recognize blurring and feel discomfort.

Therefore, in consideration of Tables 3 and 4, the value obtained bydividing the first diffraction distance β1 by the distance PP1 betweenpixels may satisfy the following Expression 8.0.1≤β≤β1/PP1≤1.9  [Expression 8]

That is, the value obtained by dividing the first diffraction distanceβ1 by the distance PP1 between pixels may be set to 0.1 or more and 1.9or less in order to balance between the effective light emission arearatio and a degree of visual blurring recognition. Accordingly, in thedisplay device according to an exemplary embodiment of the invention,luminous efficiency may be improved by increasing the effective lightemission area ratio without causing discomfort due to visual blurringrecognition.

There are no specific limitations on a value of each of the firstdiffraction distance β1 and the distance PP1 between pixels as long asthe value obtained by dividing the first diffraction distance β1 by thedistance PP1 between pixels satisfies 0.1 or more and 1.9 or less. In anexemplary embodiment, the first period DP1 and the shortest distance z2(refer to FIG. 17) between the lower surface of the first encapsulationlayer 170 and the base layer 220, which is defined as a thickness of thefirst encapsulation layer 170, may have values described in thefollowing Table 5.

TABLE 5 Case z2 (mm) DP1 (μm) 1 0.2 0.88-15.3 2 0.3 1.24-22.7 3 0.5  2-37.4

Next, another exemplary embodiment of the plurality of diffractionpatterns 210 will be described with reference to FIGS. 19A to 28.

FIG. 19A is a cross-sectional view illustrating a display deviceaccording to another exemplary embodiment of the invention, and FIG. 19Bis an enlarged view of the display device. However, descriptionsidentical to those given in FIGS. 1A to 18 will be omitted.

A display device 20 according to another exemplary embodiment of theinvention may include a display panel 100 and a diffraction panel 200_2.The display device 20 illustrated in FIG. 19A differs from the displaydevice 10 illustrated in FIG. 1A in that two refractive layers includedin each of a plurality of diffraction patterns 210_2 are furtherincluded.

The display device 20 will be described in more detail. Referring toFIG. 19A, each of the plurality of diffraction patterns 210_2 mayinclude two refractive layers having different refractive indexes. Anexample of a first diffraction pattern 211_2 will be described.

Referring to FIG. 19B, a second refractive layer 211_2 b may be disposedon the first refractive layer 211_2 a. That is, the first diffractionpattern 211_2 may have a structure in which the first refractive layer211_2 a and the second refractive layer 211_2 b are sequentiallystacked. A refractive index of the first refractive layer 211_2 a may bedifferent from a refractive index of the second refractive layer 211_2b. In an exemplary embodiment, the refractive index of the firstrefractive layer 211_2 a may be higher than the refractive index of thesecond refractive layer 211_2 b, for example.

The refractive index of the first refractive layer 211_2 a may bedetermined by the refractive index of the base layer 220. The refractiveindex of the second refractive layer 211_2 b may be determined by therefractive index of the protective layer 230 and the refractive index ofthe first refractive layer 211_2 a. A thickness t4 of the firstrefractive layer 211_2 a may be adjusted by the refractive index of thefirst refractive layer 211_2 a. A thickness t5 of the second refractivelayer 211_2 b may be adjusted by the refractive index of the secondrefractive layer 211_2 b. In an exemplary embodiment, a second thicknessT2 may be the same as the first thickness T1 illustrated in FIG. 1A.

The refractive index and the thickness t4 of the first refractive layer211_2 a and the refractive index and the thickness t5 of the secondrefractive layer 211_2 b may be determined such that reflectance of thefirst diffraction pattern 211_2 is sufficiently reduced. Morespecifically, the refractive index and the thickness t4 the firstrefractive layer 211_2 a and the refractive index and the thickness t5of the second refractive layer 211_2 b may be determined such that thereflectance by reducing amplitude of light reflected by the plurality ofdiffraction patterns 210_2 is sufficiently reduced through thedestructive interference phenomenon of the light.

That is, the plurality of diffraction patterns 210_2 included in thedisplay device 20 according to another exemplary embodiment of theinvention may include only two layers having different refractiveindexes. In this case, in comparison with the display device 10illustrated in FIG. 1A, the degree to which reflectance is reduced maybe reduced, but since the diffraction pattern includes only two layers,ease of the process may be improved and a manufacturing cost thereof maybe reduced.

FIG. 20 is a cross-sectional view illustrating a display deviceaccording to still another exemplary embodiment of the invention.However, descriptions identical to those given in FIGS. 1A to 18 will beomitted.

Referring to FIG. 20, a display device 30 according to still anotherexemplary embodiment of the invention may include a display panel 100and a diffraction panel 200_3. The display device 30 illustrated in FIG.20 differs from the display device 10 illustrated in FIG. 1A in that aplurality of diffraction patterns 210_3 are disposed to overlap only anon-display region NDA. That is, the plurality of diffraction patterns210_3 is not disposed to overlap a display region DA. Here, the displayregion DA is defined as a region which overlaps a plurality of OLEDs140. The non-display region NDA is defined as a region which does notoverlap the plurality of OLEDs 140.

Since the plurality of diffraction patterns 210_3 is not disposed in thedisplay region DA, zero-order light emitted from the plurality of OLEDs140 may pass through the display region DA. The zero-order light mayhave a relatively higher luminance than first-order light generated bydiffraction.

Accordingly, while the zero-order light is used as it is in the displayregion DA, the non-display region NDA diffracts light through theplurality of diffraction patterns 210_3 to increase the effective lightemission area, and thus light efficiency may be improved.

Unlike the illustration in the drawing, all of the plurality ofdiffraction patterns 210_3 may not be disposed in each of thenon-display regions NDA and may be disposed only in a portion of thenon-display region NDA.

FIGS. 21 to 23 are views for describing another exemplary embodiment ofthe diffraction panel illustrated in FIG. 1A. In FIGS. 21 to 23, forconvenience of description, the protective layer 230 will be omitted.

Referring to FIGS. 21 to 23, a diffraction panel 200_4 may include aplurality of diffraction patterns 210_4. That is, the diffraction panel200_4 illustrated in FIGS. 21 to 23 differs from the diffraction panel200 illustrated in FIG. 1A in that a plurality of holes 213 is definedto be recessed.

The plurality of diffraction patterns 210_4 may be provided bysequentially stacking a first refractive layer 215, a second refractivelayer 216, and a third refractive layer 217 on the base layer 220. In anexemplary embodiment, a plurality of holes 213 passing through theplurality of diffraction patterns 210_4 may be defined in the pluralityof diffraction patterns 210_4.

That is, in an exemplary embodiment, the plurality of diffractionpatterns 210_4 is provided by a method of sequentially stacking thefirst refractive layer 215, the second refractive layer 216, and thethird refractive layer 217 on the base layer 220 and then forming theplurality of holes 213. In an exemplary embodiment, the plurality ofholes 213 may be defined between a first diffraction pattern 211_4 and asecond diffraction pattern 212_4 adjacent to each other.

The plurality of diffraction patterns 210_4 may have a third thicknessT3. The third thickness T3 is defined as the sum of a thickness t1′ ofthe first refractive layer 215, a thickness t2′ of the second refractivelayer 216, and a thickness t3′ of the third refractive layer 217. Aperiod and lengths of the plurality of diffraction patterns 210_4 arealso defined on the basis of cross sections taken along a secondimaginary line c12. Since the period and lengths of the diffractionpatterns are identical to those given in FIG. 6, descriptions thereofwill be omitted.

Next, another exemplary embodiment of a shape of each of the pluralityof diffraction patterns 210 illustrated in FIG. 1A will be described.

FIGS. 24A to 27 are cross-sectional views illustrating another exemplaryembodiment of the plurality of diffraction patterns illustrated in FIG.1A. Descriptions identical to those given in FIGS. 1A to 23 will beomitted.

A plurality of diffraction patterns 240 will be described on the basisof a first diffraction pattern 241 of a display device 40 with referenceto FIGS. 24A and 24B.

The first diffraction pattern 241 may include a first refractive layer241 a, a second refractive layer 241 b, and a third refractive layer 241c which are sequentially stacked. The first to third refractive layers241 a to 241 c may have different widths. More specifically, a width ofthe first refractive layer 241 a may be greater than widths of thesecond refractive layer 241 b and the third refractive layer 241 c. Thatis, the plurality of diffraction patterns 240 of the diffraction panel200_5 illustrated in FIG. 24A differ from the plurality of diffractionpatterns 210 illustrated in FIG. 1A in that a cross-sectional shapethereof is a tapered shape.

A refractive index and a thickness t1_241 of the first refractive layer241 a and a refractive index and a thickness t3_241 of the thirdrefractive layer 241 c may be determined to sufficiently reducereflectance of the first diffraction pattern 241 and may be determinedin consideration of refractive indexes or thicknesses of othercomponents, for example, the second refractive layer 241 b, the baselayer 220, and the protective layer 230. In an exemplary embodiment, athickness t2_241 of the second refractive layer 241 b may be thethickest. Also, in an exemplary embodiment, a third thickness T_241 maybe the same as the first thickness T1 illustrated in FIG. 1A.

Referring to FIG. 25B, in a display device 50, a first diffractionpattern 251 of the plurality of diffraction patterns 250 of thediffraction panel 200_6 may include a first refractive layer 251 a, asecond refractive layer 251 b, and a third refractive layer 251 c whichare sequentially stacked. Also, the first diffraction pattern 251 mayfurther include a fourth refractive layer 251 d which is in contact withboth side surfaces of the second refractive layer 251 b. Accordingly,the first refractive layer 251 a, the third refractive layer 251 c, andthe fourth refractive layer 251 d may be provided to surround the secondrefractive layer 251 b. In an exemplary embodiment, the first refractivelayer 251 a, the third refractive layer 251 c, and the fourth refractivelayer 251 d may include the same material. Accordingly, refractiveindexes of the first refractive layer 251 a, the third refractive layer251 c, and the fourth refractive layer 251 d may be the same. In anexemplary embodiment, the second refractive layer 251 b may have atapered cross section.

Thicknesses t1_251, t2_251, and t3_251 of the first to third refractivelayers 251 a to 251 c for satisfying the above-described Expression 6may be determined as those illustrated in FIG. 25B. Also, in anexemplary embodiment, a fourth thickness T_251 may be the same as thefirst thickness T1 illustrated in FIG. 1A.

Referring to FIG. 26, in a display device 60, a plurality of diffractionpatterns 260 of diffraction panel 200_7 may have a shape in which afirst layer 261, a second layer 262, and a third layer 263 aresequentially stacked. In an exemplary embodiment, the plurality ofdiffraction patterns 260 may have a shape in which a plurality oftrapezoidal shapes is connected in the cross-sectional view.

The above-described Expression 6 is changed to the following Expression9 in the illustrated exemplary embodiment.(m*λ _(L1))−60 (nm)≤A≤(m*λ _(L1))+60 (nm)A≠{(n230−n262)×t262}  [Expression 9]

Here, λ_(L1) denotes a wavelength of light incident on one of theplurality of OLEDs 140, and n230 denotes the refractive index of theprotective layer 230. Further, n262 denotes a refractive index of thesecond layer 262, and t262 denotes a thickness of the second layer 262.A unit of A is nm, and m is an integer equal to or greater than 0.

That is, in the exemplary embodiment illustrated in FIG. 26, when thethickness t262 and the refractive index of the second layer 262 satisfyExpression 9, luminance of at least one light emission pattern of theplurality of replicated light emission patterns P1 to P8 may be about 3%or more of the luminance of the reference light emission pattern Pref.

Referring to FIG. 27, unlike the second layer 262 illustrated in FIG.26, in a second layer 272 of a plurality of diffraction patterns 270 ofdiffraction panel 200_8 of a display device 70 illustrated in FIG. 27,adjacent second layers are not in contact with each other. Accordingly,a first layer 271 and a third layer 273 may be in direct contact witheach other.

In the exemplary embodiment illustrated in FIG. 27, when a thicknesst272 and a refractive index of the second layer 272 satisfy thefollowing Expression 10, luminance of at least one light emissionpattern of the plurality of replicated light emission patterns P1 to P8may be about 3% or more of the luminance of the reference light emissionpattern Pref.(m*λ _(L1))−60 (nm)≤A≤(m*λ _(L1))+60 (nm)A≠{(n230−n272)×t272}  [Expression 9]

Here, λ_(L1) denotes a wavelength of light incident on one of theplurality of OLEDs 140, and n230 denotes the refractive index of theprotective layer 230. Further, n272 denotes the refractive index of thesecond layer 272, and t272 denotes the thickness of the second layer272. A unit of A is nm, and m is an integer equal to or greater than 0.

FIG. 28 is a cross-sectional view illustrating a display deviceaccording to yet another exemplary embodiment of the invention. However,descriptions identical to those given in FIGS. 1A to 27 will be omitted.

A display device 80 according to yet another exemplary embodiment of theinvention may include a display panel 101 and a diffraction panel 200.That is, the display device 80 illustrated in FIG. 28 differs from thedisplay device 10 illustrated in FIG. 1A in that the first encapsulationlayer 170 is replaced by a second encapsulation layer 180.

The display panel 101 may include the second encapsulation layer 180 anda second buffer layer 190.

In an exemplary embodiment, the second encapsulation layer 180 may havea structure in which at least one of an organic layer and an inorganiclayer form a single layer or are stacked in a multilayer. Morespecifically, the second encapsulation layer 180 may include a firstinorganic layer 181, an organic layer 182, and a second inorganic layer183.

The first inorganic layer 181 may be disposed on a common electrode 150.In an exemplary embodiment, the first inorganic layer 181 may include atleast one of silicon oxide (SiOx), silicon nitride (SiNx), and siliconoxynitride (SiONx), for example.

The organic layer 182 may be disposed on the first inorganic layer 181.In an exemplary embodiment, the organic layer 182 may include at leastone of epoxy, acrylate, and urethane acrylate, for example. The organiclayer 182 may planarize a step caused by a pixel definition film 130.

The second inorganic layer 183 may be disposed on the organic layer 182.In an exemplary embodiment, the second inorganic layer 183 may includeat least one of silicon oxide (SiO_(x)), silicon nitride (SiN_(x)), andsilicon oxynitride (SiON_(x)), for example.

In FIG. 28, each of the first inorganic layer 181, the organic layer182, and the second inorganic layer 183 is illustrated as being a singlelayer, but the invention is not limited thereto. That is, at least oneof the first inorganic layer 181, the organic layer 182, and the secondinorganic layer 183 may be stacked in a multilayer structure.

In another exemplary embodiment, the second encapsulation layer 180 mayinclude a hexamethyldisiloxane (“HMDSO”) layer. More specifically, thesecond encapsulation layer 180 may include the first inorganic layer181, the second inorganic layer 183, and an HMDSO layer disposed betweenthe first inorganic layer 181 and the second inorganic layer 183. Thatis, the above-described the organic layer 182 may be replaced by anHMDSO layer.

In an exemplary embodiment, the HMDSO layer may be provided through thesame chamber after forming the first inorganic layer 181. Accordingly, aprocess of forming the second encapsulation layer 180 may be simplified.Also, the second encapsulation layer 180 includes the HMDSO layercapable of absorbing stress, and thus the second encapsulation layer 180may have sufficient flexibility.

The second buffer layer 190 may be disposed on the second inorganiclayer 183. There are no specific limitations on a material of the secondbuffer layer 190. That is, the second buffer layer 190 may include aninorganic material or an organic material. In an alternative exemplaryembodiment, the second buffer layer 190 may have a structure in which atleast one of an organic layer and an inorganic layer form a single layeror are stacked in a multilayer, for example. The second buffer layer 190has a predetermined thickness, and thus a plurality of OLEDs 140 and thediffraction panel 200 may be spaced a predetermined distance from eachother. That is, separation distances between the plurality of OLEDs 140and the plurality of diffraction patterns 210 may be controlled bycontrolling a thickness of the second buffer layer 190. Accordingly,this means that the diffraction distance may be controlled. In anexemplary embodiment, the thickness of the second buffer layer 190 maybe equal to or less than about 200 μm, for example. In another exemplaryembodiment, the second buffer layer 190 may be omitted. In this case, aseparation distance between the plurality of OLEDs 140 and thediffraction panel 200 may not be sufficiently secured. When theseparation distances between the plurality of OLEDs 140 and thediffraction panel 200 are not sufficiently secured, a desireddiffraction distance is not provided and an effect of an enlargement ofthe effective light emission area ratio may be lowered. Therefore, inthe case in which the second buffer layer 190 is omitted, the separationdistances between the plurality of OLEDs 140 and the diffraction panel200 may be sufficiently secured by changing an arrangement order of thediffraction panel 200 and other components (e.g., an anti-reflectionpanel or an input sensing panel).

FIGS. 29 and 30 are cross-sectional views illustrating display devicesaccording to other exemplary embodiments of the invention. However,descriptions identical to those given in FIGS. 1A to 28 will be omitted.In FIGS. 29 and 30, display panels will be referred to with a referencenumeral 102. The display panels 102 illustrated in FIGS. 29 and 30 maybe the display panel 100 illustrated in FIG. 1A or the display panel 101illustrated in FIG. 28.

Referring to FIG. 29, a display device 90 a according to yet anotherexemplary embodiment of the invention may include an input sensing panel400, an anti-reflection panel 500, and a window panel 600.

The input sensing panel 400 may be disposed on the display panel 102.The input sensing panel 400 may be coupled to the display panel 102through a first adhesive member 310. The first adhesive member 310 maybe a PSA member. The input sensing panel 400 may obtain coordinateinformation through an external input, for example, a touch or the like.That is, in an exemplary embodiment, the input sensing panel 400 may bea touch panel which senses a user's touch or a fingerprint sensing panelwhich obtains fingerprint information of a user's finger.

In an exemplary embodiment, the input sensing panel 400 may sense anexternal input in a capacitive manner. Here, there are no specificlimitations on the input sensing method. In an exemplary embodiment, theinput sensing panel 400 may sense an external input through anelectromagnetic induction method or a pressure sensing method.

In FIG. 29, the input sensing panel 400 is illustrated as overlappingthe entire display panel 102, but the invention is not limited thereto.That is, the input sensing panel 400 may overlap only a portion of thedisplay panel 102, for example, at least a portion of a display regionwhich displays an image. In an alternative exemplary embodiment, theinput sensing panel 400 may overlap a non-display region which does notdisplay an image, for example.

Also, the input sensing panel 400 may be an input sensing layer which isdisposed on the display panel 102 through a continuous process. When theinput sensing layer is disposed on the display panel 102, the firstadhesive member 310 may be omitted.

The anti-reflection panel 500 may be disposed on the input sensing panel400. In an exemplary embodiment, the anti-reflection panel 500 may becoupled to the input sensing panel 400 through a second adhesive member320. Here, in an exemplary embodiment, the second adhesive member 320may be a PSA member. However, the invention is not limited thereto, andin another exemplary embodiment, the second adhesive member 320 may bean OCA member. In an alternative exemplary embodiment, the secondadhesive member 320 may be an OCR film, for example.

The anti-reflection panel 500 may reduce reflectance of external lightincident from an upper side of the window panel 600, which will bedescribed below. In an exemplary embodiment, the anti-reflection panel500 may include a phase retarder and a polarizer.

In an exemplary embodiment, the phase retarder may be a film type phaseretarder or a liquid crystal coating type phase retarder. In analternative exemplary embodiment, the phase retarder may include a λ/2phase retarder and/or a λ/4 phase retarder, for example. In an exemplaryembodiment, the polarizer the polarizer may be a film type polarizer ora liquid crystal coating type polarizer. Here, the film type polarizermay include a stretch-type synthetic resin film. The liquid crystalcoating type polarizer may include liquid crystals disposed in apredetermined array. In an exemplary embodiment, the phase retarder andthe polarizer may further include a protective film. Each of the phaseretarder and the polarizer itself may be defined as a base layer of theanti-reflection panel 500. When each of the phase retarder and thepolarizer further includes a protective film, the protective film may bedefined as the base layer of the anti-reflection panel 500.

The diffraction panel 200 may be disposed on the anti-reflection panel500. The diffraction panel 200 may be coupled to the anti-reflectionpanel 500 through a third adhesive member 330. In an exemplaryembodiment, the third adhesive member 330 may be a PSA member. However,the invention is not limited thereto, and in another exemplaryembodiment, the third adhesive member 330 may be an OCA member. In analternative exemplary embodiment, the third adhesive member 330 may bean OCR film, for example.

The input sensing panel 400 and the anti-reflection panel 500 may bedisposed between the diffraction panel 200 and the display panel 102,and thus an optical distance, which is defined as a distance between thedisplay panel 102 and the diffraction panel 200, may be sufficientlysecured.

As described above, the anti-reflection panel 500 may reduce reflectancedue to external light. However, when the diffraction panel 200 isdisposed on the anti-reflection panel 500, reflection of external lightby the plurality of diffraction patterns 210 included in the diffractionpanel 200 occurs. However, the diffraction panel 200 includes theplurality of diffraction patterns 210 in which a plurality of refractivelayers having different refractive indexes are stacked, and thus thereflectance may be reduced.

Accordingly, the display device 90 a according to yet another exemplaryembodiment of the invention may reduce reflectance due to external lightbeing provided to the diffraction panel 200 while securing a sufficientoptical distance.

The window panel 600 may be disposed on the diffraction panel 200. In anexemplary embodiment, the window panel 600 may be coupled to thediffraction panel 200 through the protective layer 230. In analternative exemplary embodiment, the window panel 600 may be coupled tothe diffraction panel 200 through a separate adhesive member, forexample.

A display device 90 b illustrated in FIG. 30 differs from the displaydevice 90 a illustrated in FIG. 29 in that locations of the diffractionpanels 200 are different.

That is, referring to FIG. 30, the diffraction panel 200 may be disposedon the input sensing panel 400, and the anti-reflection panel 500 may bedisposed on the diffraction panel 200. The anti-reflection panel 500 andthe window panel 600 may be coupled to each other through the thirdadhesive member 330.

Reflectance due to external light may be further reduced by disposingthe anti-reflection panel 500 on the diffraction panel 200. However, asan optical distance between the diffraction panel 200 and the displaypanel 102 is reduced, a desired diffraction distance is not provided,and an effect of an enlargement of an effective light emission arearatio may be reduced. In order to prevent this, in an exemplaryembodiment, the display panel 102 may further include a buffer layer forsecuring the optical distance. In another exemplary embodiment, when thedisplay panel 102 is the display panel 101 illustrated in FIG. 1A, thedisplay panel 102 includes the first encapsulation layer 170 having arelatively large thickness, and thus the optical distance may besecured. In still another exemplary embodiment, when the display panel102 is the display panel 101 illustrated in FIG. 28, the opticaldistance may be secured by increasing the thickness of the second bufferlayer 190.

In FIGS. 29 and 30, although the input sensing panel 400 is illustratedas being located at a level relatively lower than that of theanti-reflection panel 500, the invention is not limited thereto. Thatis, the input sensing panel 400 may be disposed on the anti-reflectionpanel 500.

FIGS. 31A and 31B are views illustrating a head mount display deviceincluding the display device illustrated in FIG. 1A. FIG. 32 is a viewillustrating a screen door phenomenon in a head mount display deviceaccording to a conventional technology. FIG. 33 is a view illustratingan improved screen door phenomenon in the head mount display deviceaccording to an exemplary embodiment of the invention.

Referring to FIGS. 1A, 31A and 31B, the head mount display device 700according to the exemplary embodiment of the invention may include adisplay unit 710 and a lens unit 720. Although not illustrated in thedrawings, the head mount display device 700 according to the exemplaryembodiment of the invention may further include a camera, an infraredsensor, a signal processing unit, and a frame that may be mounted (e.g.,disposed) on a user's head.

The lens unit 720 may receive light from the display unit 710. In anexemplary embodiment, the lens unit 720 may be disposed between anobject and the user. In an exemplary embodiment, the lens unit 720 maybe provided with an opaque lens to realize virtual reality. In anotherexemplary embodiment, the lens unit 720 may be provided with atransparent lens or a translucent lens to realize augmented reality. Inan exemplary embodiment, the lens unit 720 may be a convex lens.

The display unit 710 may correspond to the display device 10 illustratedin FIG. 1A. That is, the display unit 710 may include the display panel100 and the diffraction panel 200. An effective light emission area maybe enlarged due to a phenomenon of interference of light that may begenerated by light which is emitted from the plurality of OLEDs 140included in the display panel 100 and passes through the diffractionpanel 200.

An image of the display unit 710 may be enlarged by the lens unit 720 sothat the user may view the enlarged image. However, a screen door effect(“SDE”) may occur due to an enlarged environment. That is, for example,a boundary with the pixel definition films 130 (refer to FIG. 1) may bevisually recognized by the user due to the enlarged environment.However, a region visually recognized by the user due to the enlargedenvironment corresponds to a non-emission region.

As described above, the effective light emission area ratio refers to aratio of a light emission region in one region. An increase of theeffective light emission area ratio refers to an increase of an area ofthe light emission region. This may be expressed as a decrease of anarea of the non-emission region.

That is, in the head mount display device 700 according to an exemplaryembodiment of the invention, the area of the non-emission region may bereduced and the area of the non-emission region visually recognized bythe user due to the enlarged environment may be reduced. Accordingly,the SDE may be improved.

Referring to FIG. 32, it may be seen that an interval between the pixeldefinition films 130 (refer to FIG. 1) and the like are visuallyrecognized as a web. That is, it may be seen that a SDE is visuallyrecognized. Referring to FIG. 33, it may be seen that a degree of visualrecognition of the interval with the pixel definition film 130 isimproved in comparison to that in FIG. 32. In FIG. 31, although thedisplay unit 710 is described as including the display panel 100illustrated in FIG. 1A, the invention is not limited thereto. That is,the display unit 710 may include the display panel 101 illustrated inFIG. 28.

FIG. 34 is a view illustrating a head mount display device according toanother exemplary embodiment of the invention.

Referring to FIG. 34, a head mount display device 800 according toanother exemplary embodiment of the invention may include a head mountdevice 810 and a display device 820.

The head mount device 810 may be coupled to the display device 820.Here, the display device 820 may include a display panel having aplurality of display elements which display an image and a diffractionpanel which diffracts light emitted from the display elements. That is,the display device 820 may include one of the display devices describedin this specification.

The head mount device 810 may include a connector for electricalconnection with the display device 820 and a frame for physicalconnection therewith. Also, the head mount device 810 may include acover for preventing an external impact and preventing separation of thedisplay device 820.

That is, the head mount device 810 may be coupled to the display device820, the display device 820 may include the diffraction panel, and thusan effective light emission area thereof may be enlarged to improve ascreen door phenomenon.

According to the exemplary embodiments of the invention, an effectivelight emission area ratio may be increased.

In addition, reflectance due to external light may be reduced.

Further, a degree of visual blurring recognition may be minimized.

Furthermore, in a head mount display device, an SDE may be improved.

What is claimed is:
 1. A display device comprising: a display panelcomprising a substrate and a plurality of display elements disposed onthe substrate; and a diffraction panel on the display panel, wherein thediffraction panel comprises: a diffraction pattern disposed on a path oflight emitted from the plurality of display elements, wherein thediffraction pattern comprises: a first refractive layer, a secondrefractive layer disposed on the first refractive layer, and a thirdrefractive layer disposed on the second refractive layer; and arefractive index of the second refractive layer is higher than arefractive index of the first refractive layer and a refractive index ofthe third refractive layer, wherein the diffraction panel furthercomprises a plurality of holes in which at least a part of at least oneof the first refractive layer and the second refractive layer isremoved.
 2. The display device of claim 1, wherein a thickness of thesecond refractive layer is greater than a thickness of the firstrefractive layer and a thickness of the third refractive layer.
 3. Thedisplay device of claim 1, wherein the diffraction panel furtherincludes a base layer which provides a base surface to the diffractionpattern, and a protective layer which covers the diffraction pattern. 4.The display device of claim 3, wherein the refractive index of the firstrefractive layer satisfies a following Expression 1 and the refractiveindex of the third refractive layer satisfies a following Expression 2:n211a=√{square root over (n220*n211b)}  [Expression 1] (in theExpression 1, n211 a denotes the refractive index of the firstrefractive layer, n220 denotes a refractive index of the base layer, andn211 b denotes the refractive index of the second refractive layer)n211c=√{square root over (n230*n211b)}  [Expression 3] (in theExpression 2, n211 c denotes the refractive index of the thirdrefractive layer, n230 denotes a refractive index of the protectivelayer, and n211 b denotes the refractive index of the second refractivelayer).
 5. The display device of claim 3, wherein a thickness of thefirst refractive layer satisfies a following Expression 3 and athickness of the third refractive layer satisfies a following Expression4:t1=λ1/(4*n211a)  [Expression 3] (in the Expression 3, t1 denotes thethickness of the first refractive layer, λ1 denotes a wavelength oflight incident on the first refractive layer, and n211 a denotes therefractive index of the first refractive layer)t3=λ2/(4*n211c)  [Expression 4] (in the Expression 4, t3 denotes thethickness of the third refractive layer, λ2 denotes a wavelength oflight incident on the third refractive layer, and n211 c denotes therefractive index of the third refractive layer).
 6. The display deviceof claim 1, wherein widths of at least two layers of the firstrefractive layer to the third refractive layer are different.
 7. Thedisplay device of claim 1, wherein the first refractive layer and thethird refractive layer surround the second refractive layer.
 8. Thedisplay device of claim 1, wherein the first refractive layer is indirect contact with the third refractive layer in the plurality ofholes.
 9. The display device of claim 1, wherein a part of the secondrefractive layer is moved in the plurality of holes.
 10. A displaydevice comprising: a substrate; a display panel comprising a pluralityof display elements disposed on the substrate; and a diffraction panelon the display panel, wherein the diffraction panel comprises: adiffraction pattern disposed on a path of light emitted from theplurality of display elements, wherein the diffraction patterncomprising: a first layer and a second layer disposed on the firstlayer; and a refractive index of the first layer is higher than arefractive index of the second layer, wherein the diffraction panelfurther comprises a plurality of holes in which at least a part of atleast one of the first refractive layer and the second refractive layeris removed.
 11. The display device of claim 10, wherein: the diffractionpattern further includes a third layer having a refractive index lowerthan the refractive index of the first layer; and the second layer isdisposed between the first layer and the third layer.
 12. The displaydevice of claim 11, wherein a thickness of the first layer is greaterthan a thickness of at least one of the second layer and the thirdlayer.
 13. The display device of claim 11, wherein the first layerincludes silicon oxynitride (SiON), and at least one of the second layerand the third layer includes silicon nitride (SiN_(x)).
 14. The displaydevice of claim 10, further comprising an anti-reflection panel disposedbetween the display panel and the diffraction panel.
 15. The displaydevice of claim 14, further comprising an input sensing layer disposedbetween the anti-reflection panel and the display panel.
 16. The displaydevice of claim 10, wherein, when a width of a cross section of thediffraction pattern is defined as a first length, and the plurality ofholes are disposed to have a first period in a first direction crossinga thickness direction of the diffraction pattern, and the first periodand the first length satisfy a following Expression 1:0.4≤d1/DP1≤1  [Expression 1] (in the Expression 1, DP1 denotes the firstperiod, and d1 denotes the first length).
 17. The display device ofclaim 10, the diffraction pattern diffracts the light emitted from theplurality of display elements and generates a reference light emissionpattern and a plurality of replicated light emission patterns.
 18. Thedisplay device of claim 17, wherein luminance of at least one of theplurality of replicated light emission patterns is about 3 percent ormore of luminance of the reference light emission pattern.
 19. Thedisplay device of claim 17, wherein the diffraction pattern does notoverlap the plurality of display elements in a direction perpendicularto the substrate.
 20. The display device of claim 10, wherein: thedisplay panel further includes an encapsulation layer disposed on theplurality of display elements; and the encapsulation layer includes aglass insulating substrate or at least one of an organic layer and aninorganic layer.
 21. A head mount display device comprising: a displayunit comprising: a plurality of display elements; a lens unit disposedon a path of light emitted from the display unit and a diffractionpattern disposed on a path of light emitted from the plurality ofdisplay elements, wherein the diffraction pattern comprises a firstrefractive layer, a second refractive layer disposed on the firstrefractive layer, a third refractive layer disposed on the secondrefractive layer, and a plurality of holes in which at least a part ofat least one of the first refractive layer, the second refractive layer,and the third refractive layer is removed; wherein a refractive index ofthe second refractive layer is higher than refractive indexes of thefirst refractive layer and the third refractive layer.
 22. The headmount display device of claim 21, wherein the display unit furtherincludes an anti-reflection panel disposed between the plurality ofdisplay elements and the diffraction pattern.
 23. The head mount displaydevice of claim 21, wherein a thickness of the second refractive layeris greater than thicknesses of the first refractive layer and the thirdrefractive layer.
 24. The head mount display device of claim 21, furthercomprising an encapsulation layer disposed between the plurality ofdisplay elements and the diffraction pattern, wherein the encapsulationlayer includes a glass insulating substrate or at least one of anorganic layer and an inorganic layer.
 25. The head mount display deviceof claim 21, wherein the display unit further includes a base layerwhich provides a base surface to the diffraction pattern, and aprotective layer which covers the diffraction pattern.
 26. The headmount display device of claim 25, wherein the refractive index of thefirst refractive layer satisfies a following Expression 1, and therefractive index of the third refractive layer satisfies a followingExpression 2:n211a=√{square root over (n220*n211b)}  [Expression 1] (in theExpression 1, n211 a denotes the refractive index of the firstrefractive layer, n220 denotes a refractive index of the base layer, andn211 b denotes the refractive index of the second refractive layer)n211c=√{square root over (n230*n211b)}  [Expression 2] (in theExpression 2, n211 c denotes the refractive index of the thirdrefractive layer, n230 denotes a refractive index of the protectivelayer, and n211 b denotes the refractive index of the second refractivelayer).
 27. The head mount display device of claim 25, wherein athickness of the first refractive layer satisfies a following Expression3, and a thickness of the third refractive layer satisfies a followingExpression 4:t1=λ1/(4*n211a)  [Expression 3] (in the Expression 3, t1 denotes thethickness of the first refractive layer, λ1 denotes a wavelength oflight incident on the first refractive layer, and n211 a denotes therefractive index of the first refractive layer)t3=λ2/(4*n211c)  [Expression 4] (in the Expression 4, t3 denotes thethickness of the third refractive layer, λ2 denotes a wavelength oflight incident on the third refractive layer, and n211 c denotes therefractive index of the third refractive layer).